FWIW, I use two thinned (50/50) coats of sealer, wait 24 hours then on to the nitro. Been doing that for years and alot of refinishes, new guitars, etc.
Also, doesn't make sense why you would use sealer and then sand "back down". Is that to the wood? That would defeat the purpose of sealing.
Since I'm not sure anyone really gets the gist of what is happening I will just say this...after sanding the peghead, which is ebony inlaid with pearl "things", to 220 the inlay, filler it was inlaid with and wood is all nice and smooth. After shooting two thin coats of the sealer the epoxy seemed to raise up and feel rough around the edges of the inlay. Almost like it swelled up. I have just done the shellac and it seems to have done the same thing maybe not quite as much. I'm going to go ahead and shoot the nitro as normal and wait 3-4 weeks. If that doesn't work I'm going to be heartbroken, broke, and building a new neck I reckon.
![Mad [headinwall]](./images/smilies/headbangwalluf8.gif)