If you just want to toss paint on Valve covers anything will do ok.
The better the paint gun the better the finish but that isn't always what you need. My first gun was a Craftsman and it did fine but eventually I got a Devilbiss traditional gun (cup under the gun) and it is great. I can shoot great finish coats with it. My lesser guns have been relegated to primers. Like someone said if you get a good gun you may get brave and shoot fancier stuff. It can be fun.
Back to the valve covers. The nice guns require you to take nice care of them. I will spend more time cleaning my gun than I do shooting some panels/parts.
So if you just want to toss paint on without a lot of headache or fear of spending hundreds of dollars on guns. I see 2 choices.
Preval fillable paint sprayer.
https://store.preval.com/collections/preval-sprayerI used these to paint the undercarriage on my convertible over 30 years ago and it is still ok. Not show quality paint but it does a good job, no real cleanup and you load the paint you want in it so you pick the color.
A small cheap touch up gun can do the job a little better.
Like this one.
https://www.homedepot.com/p/NuMax-P...-with-125-cc-Plastic-Cup-SPS08/308910132Nearly everyone sells something similar, Lowes, Ace Hardware, HF, Tractor Supply, etc. etc. It isn't hard to find one under $30 and they can be cleaned and used again.
They won't give you show quality body paint but if you are looking for decent looking smooth paint these will do the job.
There are some really good qualified paint guys on here that can tell you air pressures, nozzle tips and such, if you tell them the type and brand of paint they can give you great information.
I would consider getting a good gun and try to do some work with it. You might find that you enjoy it. But for me these work well for small parts and stuff.
