When confronted with LMR, what kind of tone do you guys use to freeze out? Is it like a playful "pshhhhhhhhh whatever" no big deal attitude or rather a more serious "I'm frustatrated but being understanding" attitude?

Definitely NOT a frustrated attitude. If you notice resistance or that she's uncomfortable, just stop. You don't need to have a playful attitude or anything like that. You just stop. Just act like its no big deal.

Look, there are 2 types of LMR. There's the bullshit LMR, where the girl is just doing it, so she doesn't seem like a slut and she doesn't feel like a slut, but she actually still does want to sleep with you. And there is REAL LMR, where the girl is genuinely uncomfortable having sex at that time.
So, if you get LMR, just STOP trying to get in her pants for a minute. Hopefully, she'll reinitiate the sexual stuff, but if she doesn't then you can try to reinititate ONE more time like 10-20 minutes later. If you still get LMR the second time, then STOP and don't try to reinitate it until another day.

The reason is, if she's still uncomfortable the 2nd time, then its REAL LMR. And when you're dealing with real LMR, if you keep pushing and pushing for sex, you're gonna just make her more and more uncomfortable and ruin your chances of EVER sleeping with her.

If its bullshit LMR, then after a quick 10-20 minute freeze-out, she should be good to go.