Castor

What's a good ingredient to mix in with castor to make it sticky so it's easier to hold on to a stick when placing at a set?

Molasses

At what rate Boco ?

Glycerin. Just keep adding till you get the consistency you want. Molasses will vary it's thickness with temperature so in cold weather you'll have issues getting it out of the jar.

Not much-add a little at a time until you get the stickyness.
Molasses is also a secret ingredient in some great beaver lures,not just to improve consistency.

Won't molasses mask the castor odor?
Mineral oil will also work and It won't mask the castor odor.

Its a deadly castor additive in beaver lure.
There-one of my secrets is out.