Hello Lorriereynolds,
I've many times used PPG Seal Grip Gripper primer over wax from grease pencils and heavy crayon marks- over tar, too. It works perfectly. Seal Grip Gripper should work very well on the filler sticks because they are harder than crayons, tar & such. The wax is captured in the primer film & sealed.
Note that this primer locks on very tightly to the wood, so it will be somewhat difficult to strip that furniture down to bare wood years from now if you so decide.
Paint adheres tenaciously to the primer. And it is very low VOC for your safety.
Shellac Option:
I've many times seen my wife use shellac to seal the wax filler stick pencils before re-finishing a furniture. It does not stain well, however but paints fine. She uses shellac flakes that she mixes, but said pre-mixed shellac works.
Have Fun With Your Project!
Paul