Ok, I think I have this grit situation straight.
400 grit wet to prep for primer. Only use 180 grit as needed for scratches. Use 220 to shape repair material, and follow with 400 to prepare for prime coat Only use 80 grit for areas to be repaired Yup(cracks).
After primer use 400 grit wet again. 400 to smooth major high/rough surfaces followed by 600 to smooth surface for basecoat application
Then base/clear. Not sure what happens after the clear goes on. Wet sand again or just buff?You can wet sand any imperfections with 1500/2000/2500/3000 and then buff, or you can wetsand with 800 and reshoot the clear if it is not as perfect as you planned. Lots of options but the basics are covered.
I'll second this but say to re-clear go up a bit, maybe 1200, because it can sink if memory serves. I worked for John Connery for a few years, very respected guy in Canada, along with his brother (who actually had the fastest drag bike in Canada back then, legitimately!), but it was a looooong time ago. He's still around doing some killer bikes and cars, has a website.
Try to use catalysed putty if you have to, as well, because that red lacquer crap that air dries is nasty, sinks, does wierd crap, not to mention never dries...blah. Use a putty you can chemically harden. And as noted, 80 is for knocking down and SHAPING a rough surface quickly that's been repaired, and in those spots you almost if not always need to putty a bit...eurythane filling primer is good there
Make sure the air is super clean if it's a 'home' boothe (good filters!), especially with the clearcoat(s) AND no oil/crap shooting out of your compressor. Nice ambient temps not too hot or cold. Use a good cleaner, I believe Cleansol was the product we used, but don't quote me...right before you spray. Then brand new tackrag for every clear application (trust me, it's worth it!) and don't touch the cleaned surface with your fingers. And don't move it after you've painted it for as many hours as possible so it doesn't do wierd crap by being moved through the air. I've seen many perfectly applied finished utterly ruined because they were move an hour later when they 'felt' dry...
After primed, if you REALLY want a nice finish...mist on very dry paint, any colour, and keep sanding with 600-1200 until that mist is gone, squeegy the piece and look sideways a bit...if it's like glass at an angle, and no mist ,you can stop sanding and apply basecoat.
If you go to the effort, you'll be rewarded

And yes, I'm neurotic about this stuff LOL...
Shawn