Tongue tie released..need help/advice!

Hello everyone! My baby got his tongue tie snipped yesterday (6/27). I was told to do some stretches with each diaper change to keep the tongue from readhering. My boy hates it and tried to clamp his mouth shut when I try to do the stretches.

Anyone have advice to get through this? I'm sure he will be mad the whole 2-3 weeks I have to do it but maybe there's a trick to being more successful. I just worry I'm not doing it well.

Thanks for any advice!