Best way to smoke oil in a pipe/bong would be to light a cig take some hauls, and then tap the ash into the bowl (don't compress it just let it be).

After get some oil on a paper clip or whatever you use, heat it up and let it drip onto the top of the ash, proceed to hit it like you normally would.

Although be sparing with the flame, try to preserve it, but don't cheat yourself out of a good hit.