I like to take every scoop off from under the playfield and clean it good (Toothbrush scrub in the sink) pretty much anything the ball will ever touch needs cleaned. The underside of the playfield where the subways and scoops are need to be cleaned. I like to take the solenoids apart and clean the plungers and bottle brush the coil and sleeve (or just replace it) and wipe down the coil. All the targets need to be cleaned as they can throw stuck on dirt everywhere. Ball guides need cleaned well too and a big one grab the brush attachment on your vacuum or shop vac and clean the crap out of your cabinet! I do all this during a shop job as well as cleaning all the light boards and undersides of the inserts because I am usually installing LEDs and I still will get a little dirt showing up here and there. I will say though I shopped my TZ like I described back in 2012 during the summer and it is not nearly that dirty yet. My power ball still looks new and I play the crap out of it!

Did you clean inside the gum ball machine? Mine was filthy I remember!

Yes, I agree. I have wiped and waxed the main area of the playfield a few times since the main shop and put a little novus 1 on a rag to wipe the rubbers down. I think the new urethane post and flipper rubbers will help too because they don't flake apart like the old style. I checked last night, my TZ has 1,200 plays since the shop job.