What If I'm Starting With A Fairly Dry Skeleton?

From my experiences...
1. I'd say a week or two...I macerate around 100F and have done some mummified deer skulls in about 10 days.
2. Yes more than likely you'll need at least a few weeks.
I've had good success with mummified skulls.

 

If you have some fresh trimmings, adding a little to the maceration bucket can speed up the bacteria growth process. Some water out of an active maceration will also help jump start the process on a mummified specimen.

I too have had very good results dealing with dried up skulls.

 

Bones like what you have have already gone through a rotting process which has broken down a lot of the grease in them. As above, get them into warmed water to soak. Let them soak for a good week before poking at them. The maceration process will pick up where it left off. Any tendon material will either dissolve or can easily be cut/scraped off with a knife. If these are long bones, remember that there is/was marrow in them and it would not hurt to drill into the center hollow of the bone from both ends to allow water and bacteria inside. The holes also help later to flush out anything trapped inside.

 

Have you put anything else in the water? It should be plain water and nothing else. Check and see if the tissues are soft, If so, try doing what QBD said. See if you can add a small amount of raw flesh to the bucket, even a meaty piece of road kill will do, to see if the bacteria may get a boost. If all that was left mostly was dried tendon that might be tougher to break down completely. 3 weeks is a long time for this method of cleaning.

As for the paraloid and small bones, you can take some of the paraloid solution and put it in a smaller plastic or glass container. If you used alcohol as the solvent it will be a lot easier to find a container to hold it. Acetone will dissolve most plastics and you need to find something marked with a #2 in the triangle on the bottom. Put the bones in the solution and let them soak for a bit. You can then take them out and set them on a piece of plastic. Move them around a bit to keep them out of a puddle of the solution. After a short while they will no longer be draining fluid and you can just let them dry. If you do get a drip of paraloid where it doesn't belong, you can shave it off with a blade or even wipe it off with a piece of white cloth wet with acetone. You might also be able to stick fine pins into one part of the bone and dip the bone into the fluid. Then stick the other end of the pin into cardboard or foam to let them air dry.