This short tutorial explain how to use radar tower effectively.
Guide to Radar Tower
Radar tower does truckloads of damage and can hit pretty much the entire map no matter how big it gets.
Set it to Most Shield/Most Armor/Most Health and just let it snipe the big tough enemies while your other towers chew up the little ones.
Also you can to set the Radar to the slowest enemy, those it can hit more reliable, and those are the most tanky anyways, so the attack run isnt wasted.
Since its range is so large it power levels itself super easily, they make great work on oogie.