Pardon My Brush (1964)

Two dimwitted house painters are hired to paint an apartment hotel. It turns out that the hotel's residents consist entirely of beautiful women. The two painters inadvertently mix vanishing cream into their paint, and discover that when they paint the walls they become transparent, allowing then to observe the girls doing their daily "routines"--exercising, showering, etc.

Unfortunately the movie Pardon My Brush is not yet available on HBO Max.