Yea, holding the model will do that. All I can really suggest to prevent it is either: 1) Create something you *can* hold. I like mounting the model on two sturdy rods, and putting them into a jeweller's clamp. 2) Don't worry about the rub-off right away, because even if you touch it up you're likely to rub it off again. Wait until the model is fully assembled and based, then go back and correct the ruboff.