Re: Scratchboard sealant
If you have no alternative, you could try wet sanding the finish which may need a definite extra covering of Krylon so that you don't go through in the low spots. Then you would need to use a fine (maybe 1000 or higher) silicon carbide water proof paper to put the clear coat back to normal. Use it with a block to keep the pressure evenly applied. Nikken has the paper up to 2000 Cw. which will bring an evenly smooth finish. Try it on something else first until you get the hang of it.