I have written lines for him to say, and I am okay with posting the entire script here since it's so short.  However, if you would prefer to ad-lib what you think would sound more natural coming from him, I highly encourage it!  My husband is voicing Present Mic and may add his own flare as well, so don't be shy!

Here is the first scene (for context, this starts out with Mic scolding Bakugou for acting out after class):

Present Mic: (calmly) "Do you think you could beat me?"

or (my husband's idea)

"Sure, you're a top UA student, but do you think you can handle the big dog?"

Bakugou: "I COULD BEAT YOUR ASS WITH MY EYES CLOSED YOU FUCKING HAAACK!!!"  Maybe he continues to yell until Mic interrupts him.

Present Mic: "Prove it."

Bakugou: "Eh??"

Present Mic: "We can meet up at Ground Beta and spar."  He leans in and whispers.  "And it'll actually be allowed this time."

Here is the second scene (for context, Bakugou has agreed to go with Mic to a far off hill, where he suggests that they both do "scream therapy" to help him blow off steam):

Bakugou: "Don't fucking listen."

Present Mic: "Whaaat??"

Bakugou: "I'M SERIOUS, ASSHOLE!!!"

Present Mic: (laughs) "Not a problem!" (taps his headphones) These babies are reinforced and able to cancel out my quirk.  How do you think I don't blow out my own eardrums?"

Bakugou: "Yeah?  Well, how do I know you're using them?"

Present Mic: (SHRUGS and gives him the "what do you want from me" look)

Bakugou: "You scream too so you won't understand me."

Present Mic: "What?  Like this?" (puts his hands over his ears) "LA LA LA LA, I CAN'T HEAR YOUR EMOTIONAL VULNERABILITY!!!"

Bakugou: "GRRR SHUT UP!!"