Has anyone had success painting an engine bay with a Preval sprayer or a cheap harbor freight touch up gun with a disposable filter attached to the bottom of the gun? I'm just trying to clean all the gunk off, spot prime the bare spots, and scuff the rest. Taping off pieces I can't readily remove but the engine is out. Will use automotive paint. Obviously not looking for concours result just presentable. I don't own a compressor and would probably have to rent one. Open to suggestions. Thanks.

As you know prep is 90% of it & especially in the eng bay you would need to be triple sure that ALL traces of grease/oil/grime are out of there (even on a budget deal you want it to last/not flake off)

Sounds like a good opportunity to justify buying a compressor

I have used them to put primer and paint on small parts. I primed my engine compartment with a preval and ppg primer one panel at a time and just worked my way around doing a section of it each weekend until it was all done.

They get cold and stop spraying smoothly if you use them continuously so you'll need to spray in bursts rather than holding your finger down the whole time. If your paint is thin and has lots of metallic it may not come out all that great just because a preval can't atomize the paint like a real spray gun can.

You may be able to spray the color on one panel at a time using the factory edges as stopping points and then carefully backmasking the edges when you start in on a new panel so you don't end up with tape lines that tend to lift later on.

Yes, the cleaning part is tedious and getting old quick but I know it all has to be clean and scuffed. Got some wax and grease remover for final wipe down. I don't have a garage to work out of or I would just buy a compressor.
Just wondering about budget ways to apply paint without too much splatter.

From what Neil said I'd try that Preval (I've heard of it) especially if it comes with some compressed air source (which would solve that need/problem)

I went to the local CARQUEST and had them mix up four spray cans of the correct Matador Red for my 68 Barracuda. It went on really good. dried nice and shiny.