What to use for stripping old minis?

My coworker gifted me a big box of old chaos space Marines. Most of them have been converted to noise marines, but they are a mix of metal and plastic, and all on 25mm bases.

Separating them from the bases is easy but what's the general consensus on stripping minis that are combinations of plastic, plastic and metal and all metal?

I do have access to a ultrasonic cleaner, if that helps, Just curious on what products are safe for the models.