Like most thing in life, you need good preparation to get the best result.
Invariably this will mean removing the part.
Start by thoroughly de-greasing and removing any loose paint.
Helpful hint: A dishwasher is an excellent de-greasing device but best used when ones nearest and dearest has gone out and NOT with the normal contents!
Start with 800 then 1200 grit wet and dry abrasive paper use plenty of water whist rubbing down the surface. Where possible use a rubbing block.
Rolled up paper will get into radiused edges and nooks and crannies.
There is no need to remove all of the original paint but aim to take off sufficient to see the base metal ghosting through. Make sure to feather any edges where the original paint has peeled or has been chipped.
You should not be able to feel any steps or sudden changes in thickness.
Time and diligence taken at this point will mean you have the best possible end result.
Wash the part(s) in soapy water then rinse and thoroughly dry.
If you take the trouble to read the instructions on the can it will say something like:
Shake the can thoroughly for xx mins.
Use in a well ventilated area; it should also tell you to wear a facemask.
Don't spray near naked flames.
Apply several thin coats from xx inches.
Whilst all the above are important it is the last one that will determine the final result.
Too little paint and you will see the base substrate.
Too thick an initial application will result in runs and sags.
Too thick made up of several coats will make the paint more likely to chip and/ or crack and craze over time.
You are aiming to put on sufficient paint to cover the substrate and no more.
Use the first application as a guide coat. This will show up any imperfections remaining after your rubbing down. These should be dealt with.
You now can follow one of two paths:
1) Normal folk will apply several thin coats (leave a minute or so between then to allow some of the solvent to vaporise off) then sit back and marvel at their genius.
2) Perfectionist will let each coat dry and lightly rub down with 1500 grit before applying the next coat.
There is a third path which consists of #2 but then uses
micromesh abrasive cloth (1500 to 12000 grit) to get a mirror finish.
As to which product to use I have had excellent results from
VHT paint which has proven very durable and still looks good after ten years or so.
Note that this need to be cured which can be done in the oven or using the heat from the motor.
If doing #3 above cure before final finishing.
There are also other engine paint which are probably just as good and I'm sure others will chime in with suggestions.
