Got it! The secret was too easy to be proud of it.
Take a plain macchiato glass.
Fill with milk.
Put under the steamer.
No moving, no fiddling round with cups, nothing.
Gonna hit another fleamarket tomorrow.
Started ripping my mags, only keeping the pages I really fancy - definitely need space.
The rest really doesn't deserve mentioning.
A bit more than half-a-year without a dishwasher.