I've had some success with giving rougher paint finishes a go over with Car body cutters like T cut.
If that fails, after the light rub down and degrease, you can respray using Krylon satin black weapons paint.
A new forend shroud is easy to get hold of, even the earlier Webley and more desirable Beeman version which is the least garish are held at Knibbs Country store Uk and Proteks Uk has later Spanish versions.
Source some wood grips maybe.
First clean the barrel and degrease the cylinder.