I'm sorry, I'm confused. Why is he getting behind from writing up work, but he doesn't perform it? Does he just briefly write down " lie front brakes, bad idler, bad pitman, leaking radiator ?) or is he doing that and putting estimates together?
To answer your question, at my shop all my guys are either hourly or the foreman is salary. If we ( the techs) turn a certain amount of hours I give them a bonus ( which is 1099 so it doesn't raise my work comp). Then if the total labor hours for the shop is sold at different levels they get an additional bonus on that ( ie 400 hrs gets $250, 475 $375, 525 $500).
It's worked really well because we all work as a team and everyone wants to get the shop the higher hours which a is stagger so I make the lions share of the money but techs get a nice bonus (up to $1000 extra/ month)