It might seem a little silly or obvious to ask this, but I wanted to know more. What are the best reactions to getting a pie?

Depends on the scene and if you're acting out a scenario or not.

Personally I like unhappy/comeuppance style unhappiness.

Look shocked, at first. Then pissed off. Depending upon whether or not you curse, perhaps some profanity. Then start laughing. LOL!

I like to see natural reactions, I've always enjoyed the videos of women getting pied for the first time, probably as there's little room for acting when it hits. Or laughter and fun.

A great first reaction for me is to have your mouth wide open in shock and/or disbelief and/or outrage - and/or ecstasy.

Unless you're a really good actress, don't try and "act" in any way. It always seems to come off as unbelievable. You are being hit in the face with a pie. It's a pretty funny and ridiculous thing. When a model has natural laughter that is authentic, that is by far the best reaction in my opinion. Frankly, I don't like when the model act as if they are disgusted or upset or pissed off in any way, but that's just me. Just try to have some fun! That's my advice.

I agree with that it should just be your natural reaction, for me I enjoy it most when there's the laughter, giggling at how fun and silly it all is. Definitely don't want to see people not enjoying themselves, that takes me out so quickly.