Looking to grind out Engineering XP, but can't be bothered to spam grenades? I've got the solution for you!
Guide to Grind Engineering XP
Let's Play Minesweeper!
So basically, there is a minefield out in the Badlands (the wide open area on the East Side) where there are at least 100 plus mines just chilling around; you come here naturally to solve a gig (sidequest) in that area. (Note that you must have encountered Silverhand in the story before this area is available) Here is an in-game image of me in the minefield.
Each mine depending on the technical ability (lvl 3 and 7) required to defuse it gives you varying amounts of engineering XP. I'm also fairly certain they respawn after a time, so if you have a lot of time to waste, feel free to grind out the mines until you have max XP.