I have found that with a clean and close fitting joint, Titebond II gives a much more undetectable repair than any epoxy I've tried. Also, Titebond II provides a repair joint that is stronger than the wood if used correctly. Titebond III works great too.
Open the crack as much as you can without making it worse, and use compressed air to blow out any debris that may prevent the crack from closing completely. By all means use acetone or other solvent to clean the crack if it is contaminated with oil. Of course, the use of solvent may remove or damage the stock finish, so refinishing may be necessary. Do your glue repair as quickly as you can after cleaning any oil in the crack because oil will slowly continue to come to the surface for many weeks after de-oiling. Let the solvent dry before gluing. You can also use compressed air to blow the glue deep into the crack, but cover things up with an old rag or towel to avoid blowing glue all over the place. A good glue joint will be completely coated with glue, and then carefully clamped tight enough to close the joint. But not so super tight as to have excess squeeze-out, and starve the joint. Use a wet cloth to clean up any glue that squeezes out onto the surface, into checkering, etc.
Strips of inner tube or rubber surgical tubing works well for clamping irregular surfaces. You can lightly coat the tubing or rubber strips with furniture wax to keep them from sticking to the wood, if you are careful to keep any wax out of the repair joint.
Clear epoxy is a better choice when there are any gaps to fill. But the repair joint will be more visible, and it will take extra work to try to hide the repair.
