What is the best way to het in and clean these?

Think I have s*** right down at the bottom from when I removed rust with a dremel so want to get it nice and clean before refitting.

Currently I have left then soaking in the garage with brake cleaner squirted into them. Before getting a screwdriver and a bit of rag and trying to pull all the gunk out (if possible)

I do as you have described but I also use a long round metal file to clean up the surface inside, then blow it out with an air duster.

Awesome, at least I am off to a good start

I can't see any rust inside the barrel and the slide pounds still move perfectly fine, it's just a few small flakes of paint. Mixed in with the grease.

if the pins have rubber bushes on(not obvious)   don't use ordinary grease they will swell and bind    use "rubber grease"

Use a drill bit as big as you can while still having a bit of movement and twirl it in the hole with your fingers. Usually 10 or 11mm.

I used to use the red rubber grease but found it dried out quite quickly so just go for the nice clear stuff now that's still slidey two years later.