Here is my limited response:
Most experienced users say IPA/Acetone is terrible at extracting alkaloids from the plants; most users suggest extracting to freebase "crystal/powder" form. There are a few teks in the wiki and throughout the forum. This is the recommended route.
Many people just let the caapi soak for 4 weeks in the IPA. Hold the jar to the light and see that the solvent shines a dark red when held to the sun; that's when it's ready.
You only need enough solvent to cover the material. Shake it every so often.
If i were you, i would do each of the herbs in different containers and then mix in the desired ratio once it's ready because they each offer different qualities that you could experiment with.
The 10x for sure makes a difference with Caapi; it becomes "ayahuascaesque"; much more powerful. This is many people's preferred form of changa.
I can't comment on 10x of other herbs, as i haven't tried it nor have i read about any enhanced effects with it.
Try it out, though, and let us know what each adds to the experience!
goodluck