sand cowl with fine wet and dry sandpaper and wipe down with panel wipe (methelated spirits will do), get automotive aerosol paint primer and give a couple of very light coats, sand off any runs between coats (you should be aiming to get no runs if you are your coats are to heavy),let dry fully and sand lightly then panel wipe, and then spray with automotive aerosol colour of choice, use light coats and let dry and wet/dry sand any inperfections between coats.

automotive paint is fuel proof but you need to let it dry in a warm place for a few days to totally go off, a clear coat of automotive paint can be added to bring out some colours but is not needed.

Basic rules I use are sand to key, lots of light coats (patience is required) and let the primer dry fully before top coat and let the top coat dry fully before handling and fitting cowl.

Automotive paint is great, loads of colour choices.

Maybe there is better products ot there or better ways of doing things but this is what works for me.