Mike - I've found that in many instances a water-based industrial degreaser works as well as or better than solvent. I use
Purple Power because it's readily available locally to me, and it's a lot easier to get rid of after you've used it up than solvent (I'm in California, and the Powers That Be are a lot more fussy about dumping solvent/oil/etc. onto the ground). I use spray bottle of Simple Green for smaller parts that I clean off in the sink (when SWMBO is not around to catch me...).
If you decide to treat yourself to a real parts washer with pump and all, you'll find that nowadays most are not rated to use solvent in them.
If you live in a city or don't have a power washer yourself, your friendly local do-it-yourself car wash will be your friend for the really yucky stuff. I spray with
Gunk, then take over to the car wash and have at it with the wand and high pressure soapy water. Washes the bulk of the yuck into their catch basin and you're left with at worst a light coat of grease that you can easily remove.
Oven cleaner is good, too.
Both Gunk and Purple Power (or something similar) should be available at your local big-box or auto parts house.
Beware that many of these products do NOT like anything other than iron or steel because they have some acid or alkaline properties. Plating, pot metal, aluminum all can get eaten away. (I destroyed a set of motorcycle forks figuring that out.) For those, simple paint thinner is probably your best bet.
On another note - as you go through and clean things up, think about treating your parts to a rust converter step after you clean but before you repaint. I use
Evapo-rust and other than it usually taking a lot longer to work (up to overnight) than the product data suggests, I'm quite happy with the results.
JayJay