I can’t imagine a situation where it can be useful, but I don’t play competitive, so for anybody who does, give me your thoughts on the matter.
Burn up is actually good. I almost lost to a fire monotype trainer who had burn up in some of his Pokemon. Luckily I had just added a rotom-wash so I won(somehow). It only has side effect of removing fire type from the Pokemon. PRO- no weakness after that CON-no stab on fire type moves(which can made up by only switching out it is almost like outrage, whose confusion can be cured only by switching {almost okay?}) Its a good move as I can make out but I never used it. Hope I Helped!