Is it legal to push the rook with the king when castling? I've gotten into the habit of pushing the rook over to the appropriate square using my king; that is, I take my king into my hand, I take it to the outer edge of the board, then push the rook to its right place using the king figure. Then, I place my king on the correct square.
I've not played in an over-the-board tournament before, and if I ever do so I'd like to know whether this is okay or whether it's a habit I need to lose.
As long as you -

only use one hand
touch the king first
don't do it in such a way as to disturb the opponent

then it is fine.