Ok, this is what I would do. I spray cars as a hobby but as of yet have not needed to repair a scratch on its own, usually the panels are sprayed entirely.
1: buy some, G3 rubbing compound,
If you only have a can of the base colour then I assume you should also have a tin of lacquer, also. If not then you will need to purchase a small amount of lacquer as without it the paint will wear off. and will look dull in appearence. You will also need a very very fine/tiny headed artists paint brush.
Or leave the tin on the shelf and buy a 2pack touch up pencil kit. This has 2x bottles 1 colour and 1 clear lacquer. Can be baught from Halfords for around £:10
2: rub over the scratch with G3 compound on a damp clean rag, this will remove any contaminants and debris. buff off with a clean cloth.
3: Apply paint to scratch applying as minimal amount as possible. If you are using the paint from your tin then stir the tin for 5mins minimum and tip some paint into another small container. Maybe thin it so that it is 10% thinners and 90% paint. (Thinners are used to a 50% mix when spraying through a spray gun.) Stir the paint again.
4: Apply paint. Apply as little as possible just get a little paint on the end of the brush and try to only get it in the scratch.
do not try to get it in one go. leave to dry for 20 mins then apply some more (very thin coats) You should not aim to build your paint up to the same level as the original paint ( remember you still have to add lacquer) the paint should be enough to have covered what was underneath.
5: leave to dry for 3 hrs. then use a 2000 wet n dry keep tear off a piece the size of £5 note fold it in half then use. keep wetting it in a bucket and very very gently rub over the scratch lightly.
6: dry bonnet off. Must be 100% dry on treated area. Then add lacquer in the same careful way as the paint. (lacquer does not need thinning) leave to dry for 12hrs.
7: wet and dry in the same way again to ensure lacquer is same level as paint. dry bonnet off and look at the terrible hazing/scratches the wet n dry has inflicted.
Rub over scratches with G3, buff away. Until they are all removed. Then polish bonnet.
