Wooster black bristle brush. Painting metal requires more than one coat if you want it to look nice. I actually like foam brushes for this type of work, but as I said, the second coat makes all the difference.
This. You gotta do more than one coat.
I love Rustoleum, I think it's the highest quality, readily available, quality paint for the DIY-er. You can buy it on any Sunday at Ace, HD or Autozone. It's not terribly picky about surface prep, and is extremely durable IME.
If I'm brushing it on I don't thin it at all. If I'm spraying it, I thin about 50%.
I rarely spray anymore because I don't have a paint booth and overspray is a PITA. By the time I set up to spray I can just as quickly brush it on, PLUS I'm often painting things like horse panel, crusher screen and expanded steel where overspray becomes EXCESSIVE.
Also brushing you can usually get away with just two applications (because it can be brushed on so thick). Spraying will take more than two applications.
I disagree about Krylon being worth a darn. On at least three occasions I've seen it fade, chip or peel badly within days or weeks of application. Maybe I didn't prep properly - but that's the whole point - - Rustoleum lets you be lazy about prep and since I'm not painting show cars I'm not picky.
For those complaining about dry times the Rustoleum Professional stuff dries MUCH faster, but color selection is limited - altho the black is a hit for bumpers, headache racks, trailers etc.
The Rustoluem Universal is ****, I'm not sure what they were thinking with that.