Guide to Solo Daybreak
Useless Melee Weapon
The melee weapon consumes three things; carry weight, stamina and time. You should never use it as you can dodge behind them and stab them in the back with a knife or floor them with a shot and stab them in the face which is a far quicker animation than the melee one.
Some people think the CLEO blast rifle is the best weapon, its ok but not optimal for daybreak. You are facing an army and you need a weapon with spread, power, knockback and good ammo consumption. Thats the CLEO shotgun, it will kill most enemies other than the jug in one shot and floor anything it doesn't. Thats where the knife animation comes in handy for armoured zeds.
Remote Rocket Pod
This is the most powerful item in the game. Anything in its area of effect dies, pure and simple. You need this for wave 5 for the two blood jugs because you need them dead fast so you can kill the hordes coming in. If you don't have this try using a minefield or, at worst, a remote explosive. WARNING: Do not try to put one directly underneath a horde or jug. It will place it off your target and potentially miss entirely. Try to put it alittle to the side so it remains in the area of effect. This has cost me many rocket pods.
Two NPC's with hordebreakers
You can do it with two guys with shotguns, I've done it. I'm telling you not to and that they are worse than useless. Guys with hordebreakers take care of business and ferals... usually.
Paranoia is good
First off, your primary thought here should be "If I don't know theres something behind me, there probably is." Guns make sound and sound can attract zeds away from attacking the walls. If you think something is behind you dodge backwards, shoot or stab them in the back. Snacks and pills may be occasionally handy to deal with the consequent stamina drain but you will almost never need them. This is why ditching the melee weapon is good, saves you stamina and more important; time. Also; RUN WHILE YOU RELOAD to avoid interruption and frustration.
Oh and you can repair walls in gas clouds by dodging into them and interacting. Time is more valuable than health. You can get medkits, you can't get time machines.
The calm before the storm
The time at the start where you have to prepare is the most important. You need to go through every box, take it all out and drop it infront of the barrier in an organised fashion as quickly as possible for easy access. It will be your job to predict what you need, when you need it and what you should put down so it doesn't take up space. I *highly* recommend putting the CLEO ammo and bandages found here near the tech for wave 5 and beyond. This will be your emergency supply. Any other CLEO ammo you find in supply drops you should put where you like outside the walls.
You will be using the hordebreaker for the first wave, normal shotgun for the second (and third if you feel confident) and the CLEO shotgun for anything past that.
After the last zeds of the third wave die your organisation skills pay dividends; you're going to make repairs then run like crazy and collect ammo, explosives, medkits and bandages after every wave. You're going to drop all your stuff, get all that, come back, quickly organise what you don't need, pick up what you do.
The storm before the hurricane
For wave four its pretty hectic but manageable, use explosives to kill jugs, use fire bombs to blow up gas clouds, use your gun to kill things as fast as possible. Repair as soon as the last zombies hit the ground, don't heal. If I remember correctly; the only ammo you will find in the supplies is in CLEO pistols, you can empty them into your inventory without having them in your inventory. The rest is mostly medkits and repair kits. Useful but... yeah. You're in trouble. Heal as soon as you get one, run back, pick up ammo, rocket pods, whatever else you think you might need.
What makes wave 5 so bad is the overwhelming numbers you're up against versus the total lack of raw firepower you need... without the rocket pods anyway.
Stick to what I've told you so far and you're good. Kill Jugs with the pods and gas clouds with fire bombs but even if you do this theres a possibility they could break through. If this happens your primary strategy will be to clear the ones that are on the technician while using your now internalised paranoia to dodge zeds. The shotguns power and spread really shine here and the tech is immune to friendly fire so thats good. Time your shots, reload when you can, do whatever it takes.
When the last one goes down you have got past the worst of it but there is still more.
The supply drops from here on out are extremely generous. Prioritise explosives over ammo. Use them the way you have learned. Lay the mines outside the walls if time is running low and inside if you got afew seconds spare. (Be aware that you can be knocked over by exploding mines so be careful... also if you launch the mines directly beneath a jug they all hit and explode on him killing him instantly. Ferals are also killed instantly by mines. Something to think about.) If you have survived wave 5, repaired the walls and got the supplies you want then you are in very good shape and you're close to winning this. Wave 6 is mostly zeds with afew jugs thrown in but nothing you can't handle with your remote explosives.
Wave 7 is afew zeds with a crazy amount of jugs and ferals. But theres good news, when jugs aren't coming your direction theres an opportunity to quickly blast away afew zeds and repair that wall while stragglers helplessly pound on it then hop back over to put shells in their faces and turn to the coming jugs.
Oh and one more bonus; you don't even have to kill them all. You just have to survive until the wave ends. I mean, you definitely should kill them all and I will see it as a personal insult if you don't but that is an option. A highly dishonourable option that we will all judge you for.