"decent but cheap" spray paint

I've used Rustoleum industrial enamel spray paint with good results
recently. It's like $5 a can. Only a very limited color selection.

Auto paint stores can put really good paints into spray cans with
custom color mixes if that's what you need.

I'm not sure what sort of structure you've built out of the angle iron,
but I've always found it easier for structures to brush on a good
enamel than to spray and miss, especially if there's an "inside" to the
structure that must be painted too. For something that's made out of
angle you don't really notice the brush marks that run the long way.
For a big flat area spray paint lets you avoid the brush marks.

Tim.