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.
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 the natural reaction. Usually a combination of surprise, laughter and acceptance with a subtle head nod and smile. Don't wipe it off too quickly, but after a pause maybe a slow 2 finger eye scoop and flick the cream away.
Generally I'm laughing throughout thr whole pie process. We use colorful foam pies and I love the feeling of hoe the foam builds up on my face , chest and head. Sometimes we get really kinky and my Pie Domme just smothers me with foam pies and voice is muffled. Many times , I just enjoy the pies as I keep getting them shoved in my face.