I got a big Ozuku a few days ago and have been sealing it with shellac. It was coated around 5-6 times I think with a little over an hour between coats (the container said to wait an hour between coats). The stone needed a lot of lapping work done, so I decided to do that earlier today, about 18-20 hours after the last coat of shellac went on. After lapping in slightly warm water, I noticed that I was leaving a ton of fingerprints in the shellac. I switched to colder water, but I was still putting fingerprints in it. After the stone dried, the shellac looks really thin and 2-3 small areas have wrinkled and come off. The sides are really wrinkly, thin, and dull looking whereas the untouched areas are glossier. Even those areas are easy to mark with fingerprints.
Anyone know what's going on? Do you know if I can use some other kind of sealant over the shellac that would be more waterproof and ok for the stone? I was going to use water based polyurethane, but the terrible hardware stores near me don't have any.

Oh and the shellac is Zinsser Bulls Eye Clear Shellac