Hi 333-blue,
From what I observed, if you already have only 2 TMs, don't use them first. Keep in mind that TMs is recommended to be used on your Pokemon that will be oftenly used during raid or gym battle.
You can invest on your best pokemon, best is means has IV>85%, and current pokemon which is useful in this current metagame. (i.e Tyranitar, Alakazam, Dragonite, or even Lugia).
But if you insist to use your TM, you can change the machamp moveset. Heavy slam did not get the STAB bonus. Good luck