I would recommend leveling whatever your lowest weapon is. Try to get all your weapons up to the same level and then level them all at the same time. Bosses are great for this--take a crew for healing AND a crew bonus, or just find a good spot where you can attack a boss without taking too much damage (cliffs, second stories of buildings, etc) if you're going solo. I'm not a big fan of glitching into a wall, personally.
If you do it right with the right enemy, you can get 100+ points for each weapon you use on an enemy.
Check out
this thread for the details.
Good luck, mate!