I think the best way to answer those is the following;
1) Make sure that the clam tends to spend as little time as possible in the air, and you place it relatively similar to how it was in the prior tank/setup.
2) I never have but I don’t see how a soft brushed toothbrush would do any damage (personally).
3) Slowly and gently wiggle/pull the clam, do not use force or grab it with crushing like grip/force.
Good luck!