Hi Art,
If your resin is gooey after the cure time, you are going to need to scrape it off/out of the surface. If it’s simply a little sticky, you can recoat it, but gooey won’t work. 🙁
Yes, a clear coat of epoxy over another layer of resin (either clear or colored) should cover up scratches provided they are minimal. If you are talking about scratches left by sandpaper, you need to end with a 1000 grit or higher in order for the scratches to be covered.