Differential question

[Zeroman]

So, I picked up a used differential a couple of weeks ago. Ring and Pinion gears look in great shape, but it was in pretty sad condition on the outside...rust, dirt, etc.

I pressure washed it, sand blasted it(now I know why people pay "other people" to sandblast!), primed, and painted it.

Planning on popping the cover back off of it again, pulling the axles, replacing the axle bearings and seals, and replacing the pinion seal.

Should I "flush" the differential and clean out all the old gear oil, and possibly sludge, that does not drain out? If so, how should I do it? Do I use a solvent? What kind of solvent?

Anyway, thanks in advance for any advice.