I have a wave gage, but frankly it's only good to put numbers on Dicks flight test reports. One needs to watch closely for a rapid change, then go back and find it by feeling by hand............if you can feel a bump, it needs to be dealt with. I have filled a spar depression with gelcoat, leveled the wing, masked off the depression, sprayed on something like 6 coats, let it cure for 12 hours, then block-sanded it level using 400 wet, then 600, then buffed it out after curing for a week. Worked well, the big problem is in matching the color exactly, so your efforts don't show.
JJ