A quick search using in the Framebuilders "Search This Forum" for painting in the thread title yields about all you need to know:
https://www.bikeforums.net/search.php?searchid=16897863
You might read the threads and then ask questions if you still have some.
One of the biggest differences (the biggest probably) is you need to use an etching primer on bare aluminum. Steel really doesn't need it. I'd use (have used) auto-paints. If you're doing the work, it doesn't make sense to use cheap paint. Read the threads in the search above...