I don't really get the second part. Who smacks their iron?
When it get's hotter you still want to estimate the heat of it you slap it quickly to deduce what temperature it has reached and whether it has become hot enough. It is just impatience, but it could be that he doesn't have anything to hold the iron up while it heats up (safely at least).
I was confused at first but I think the boobs are supposed to be the nob for the temperature setting. With how she's positioned though the nob should be her head but meh, gotta have the perviness in there somewhere.