Hi Greg,
I spent a lot of time experimenting with this on my LP build. What I found was:
Yes, the witness lines will disappear with the last coat but only if the sanding grade is very fine. I found that I could only achieve this once I got to 1600-2000 grit or a mild fibre scouring pad. Even then, if you use sand paper with folds in it or raised areas from poly build up this will set you back. Changing the paper every 10-15 seconds did the trick, or for something that lasts a bit longer, 0000 steel wool but that is problematic because it leaves a lot of steel particles behind in the process. Fibre pads left the least amount of breakdown for me..
Don't sand the first few coats of wipe on poly if you use it. If you sand through the thin layer and affect your stain or paint in some way underneath its very difficult to fix. I like Feast-Watson Wipe On a lot but you have to be very patient and put aside at least a week for it.
I did ten coats of wipe on ploy over a week and that was pushing it
Then applied 4 coats of Cabothane. Cabots clear gloss poly spray, and found that to be a good product. Last coats laying flat. 2 weeks all up for finishing.
Yes! If you're patient (which I'm not so it was the hardest part for me) and accept the fact that a high gloss finish takes time without the use of compressed air guns etc then you're all good!
