He might need more than clues, littlek. Put a laminated note in the
bathroom (preferably next to the mirror) with the rules.
1. Reduce all noise.
2. Always flush and keep the seat down
3. Clean the sink and shower after you used it
4. ....
I draw a blank here, as I never had a roommate. Spouses are so
much better to deal with and train.
You and dagmar have lived together for quite a while, you're friends
and you know each others habits. Mr. Portugal is new and needs to
learn, as he's apparently clueless (pun intended).