Rashi on Leviticus
משכבי אשה means he inserts as a brush into a tube [i.e. in the manner of marital intercourse].
Siftei Chakhamim
One inserts. Because if not so, why write “in the same manner as with a woman?” Is there another way to lie with a male that the verse has to say “in the same manner as with a woman” in order to exclude this other way of lying?
Chizkuni
משכבי אשה, intercourse in the full sense of the word, not fondling or premature withdrawal of either party’s male organ.