Best approach / products to repairing paint work on scuffed GRP Hull

[Gilaroo]

I just took my 17.5 ft fishing boat out for engine service anti fouling etc..
While at the marina one of my fenders got lose and mid port side of the boat was scuffed (photo attached). There is blue scouring and grey discoloration in 2 areas but not over a large area where the boat came in contact with the jetty. There is not any cracking but the areas feel a little course from the rubbing, however there are not any serious cracks in the GRP. I have powered washed the boat today , let it dry and then tried white spirit rigorously. No improvements were made and both grey and blue scuff are there and look bad. Has any one got any suggestions how I might repair this to a nice white GRP finish again? What products might work.

Many Thanks Gilaroo

Hey, Gillaroo. Sorry 'bout the damage to your baby. You say that there was "no serious cracks in the GRP" - is there ANY cracking? To me it looks like not, and I'll go on that.
I can't really tell but from the pattern of the right-hand rub, it looks like the boat has a white paint over black over white gelcoat - does that seem correct? If it is rubbed thru the paint, there is only one option and that is to match color and spray repair - just hire a pro painter. The blue scuff could probably be buffed out and things, in general, could be improved but there seems to be irreparable damage to the paint.
I'm sorry but I am sporadic on the site and can't reliably check on your progress. I guess I would start with a little abrasive - carefully wet sand with 400grit paper with just your finger tip. That will likely get rid of the blue and when you go to do this, you can look closer at the right hand damage. If it is, indeed, thu a layer, there is no substitute for a pro paint repair. If I am seeing it wrong, and you can sand it down to white, then almost clean it up with 400, then continue thru the grits to at least 600 but with a sanding block, then buff and wax. You could go to finer grits but I don't think we're fixin' a Steinway here. Good luck - I'll try and check in later.

First try Magic Eraser. Some place called Maplins carries it in the UK. Be advised that it removes material, as well.

[Gilaroo]

Many thanks Mark. I think you are right, the paint layer on the right mark must be gone and the grey is the next layer. I'll try to source a painter to repair and try some other products on the blue scuff