simple first, sure, you can blast your hinges.. just make sure to blow/work out any sand from the pivot area...
now the tougher one....
first, ANY part, whether a hood, air cleaner, wheelwell, door, etc will benefit from a proper coating procedure.. in other words, no matter what paint you put on a zinc/fill prime process prior will make it that much more durable..
for example, full load of blasted parts..
zinced
then 2k urethane primer.. can't seem to find that pic...
as to paint...
here's my take on blacks... gloss is a challenge.. it can look very, very good... or it can look very cheesy if the time isn't taken to make it look right... it's also very durable and cleans up well...
satin is usually my choice... i feel it looks the best.. hides minor flaws much better than gloss... cleans up ok and is relatively durable...
flat... not a real fan of... looks cool when ya first do it, but cleans up very poorly...
what kind of paint... all the same rules apply.. obviously a catalyzed, thru the gun urethane will be the toughest.... gloss, thats no big deal... satin is vastly more difficult and unpredictable due to flattening agents... I run flattened black Imron on my stuff.. I do not recommend it for most... and obviously it can get pricey with hardeners, reducer, etc...
good results can be had with rattlecans, albeit, limited in durability due to the air-dried resin.. I achieve excellent results at work with standard satin black rustoleum rattlecans... very consistent and leave a good satin...
this stuff...
it is only an enamel, so somewhat soft, but it's relatively tough... there are quite a few satin rattlecans on the market tho.. you could try a couple different ones and see which finish you like..
wheelwells should be treated the same as any other part... prime and paint inner and outer..... you can add an undercoating to the roadside after the fact for some added protection... 3M has always made quality undercoatings...