[rossdavidh]

So, no claims that I'm an expert at this, but...

The part-time thing has two kinds, in my very limited experience. One, is doing maintenance on something you used to work on full-time. You already know the code base, you just don't need to be doing full-time work on it. If you were good to work with, previous employers might have a use for you on a part-time basis.

The other kind, is going to be the fiverr-type thing, where your pay rate is not competitive.

So, leveraging past employment (or coworkers who went on to other places, who know you know the thing they need a bit of extra help on) is, again in my very limited experience, the way to do it. One more reason to be nice to people, even at places you have decided to leave, or they have decided to leave.