Hi, I am skinning an item in carbon fibre.

I have laid the carbon and sealed it with 3 layers of resin which is fully cured. I always use 400grot paper here to completely flat out the surface before one final thin  coat of resin.

I have been unable to sand out some of the low spots with 400grit. My question is, how low can I go in terms of sandpaper grit here? Will a coat of resin hide the scratch marks of a 200grit or maybe even a 120grit paper?

Thanks in advance for any help you can give.