Just so nobody misinterprets the last post-do not sand clear with 220 grit I understand the question with the reference to 220 to be for undercoats/primer surfacers and fillers?
There's no rule or guidelines set in stone that I follow. On small to medium repairs I'll often break and rough in filler with 80 stopping short of perfect contour then switch to 180, then sometimes apply guidecoat and finish it off with 320. Polyester primer I have started with 80, guidecoated then switched to 150 or 180 or 220, applied guidecoat again and sanded again at 320 or 400-all depends if the shape is right and enough build is left. Urethane surfacers I'll start with 180 or 220 on big jobs and sometimes 320 or 400 on smaller jobs and sometimes apply guidecoat and finish with 600-same with epoxy. Think of it this way:if your contour is right at 80 grit you should have no problem resanding with a finer grit to the bottom of those 80 grit scratches while still maintaining the right shape. Grits I keep on hand: 36,80,120,150,180,220,320,400,600,800,1000,1200,1500,2000,2500,3000 and some get used more than others but they all have their own purpose. Another thing to think about when colorsanding: If you're using a good flat block or high density contour pad and removing minor orange peel (not urethane wave) you can stop sanding with the coarser grits before all the peel is out and still maintain straightness. If there's a trace of shiny specks left showing the peel hasn't been completely cut out but say 90% that's OK, use them shiny spots as an indicator of when to stop with the next finer grit and it'll also leave more clear on the car.