P2P is a neutral ketone, while meth oil is a basic amine. I can think of these three approaches:
1. Use it all up in the reaction. That is not going to happen, because the reactions of this material are quenched in a thermodynamic sense, to my understanding, which means that an equilibrium state is the final state, and product changes back.
2. Leave it behind in the isolation step of oil. That is not going to happen, either. Steam distillation drives P2P over, too.
2a. P2P can form a solid derivative, a bisulfite addition product, or a phenylhydrazone. Maybe you can decant or filter.
3. At the gassing stage, when the meth oil is treated with HCl, the P2 will not react and will stay liquid. Then it is removed with an acetone wash. They are both ketones. Like dissolves like. As you rinse the crystal mass the yellow color will disappear, but to get it white-white, it will take half your product with it. So, most people leave the product with a slight yellow tinge. Methamphetamine hydrochloride is a white solid, so, I never liked putting that yellow material in my body. Light yellow product I believe turns a darker yellow with time. A discussion of drying acetone is posted on sciencemadness.com. I told them it was for washing meth, and they gave me a bunch of lip and banned me on speculation.