Since it's a beater, a rattle can job should do. Remove as much surface rust as you can. If you can remove it all, great. Prime with RustOleum Rusty Metal Primer or equivalent. Finish with color of your choice.

In all kinds of spray painting, remember that several light coats are better (smoother and more durable) than few heavy coats.

Be sure to follow the "user manual", i.e. the directions on the can! 99% of all paint problems can be avoided thus.

Look into the "hammered metal" finishes by RustOleum and other brands. I like the look (YMMV) and it is quite durable. The finish covers a multitude of sins. I've used it successfully on outdoor steel furniture & it lasts years out in all kinds of weather. I am planning on using this for my beater once it's warm enough to strip & paint in the garage.

Of course if this were a "nice" bike we'd be talking catalyzed automotive finishes or powdercoating, both of which are usually best left to pros IMO.

Markham sounds familiar. Are you near KW or TO? Lots of nice roads & paths around KW/Guelph/Wellington I'd like to try on a visit.

(EDIT) +1 on Retro Grouch's words of wisdom too. There's a difference between "dry" and "cured" paint; curing is what hardens it and that takes time.