Lessons from repainting a room's worth of trim: caulk and clean before paint, slide a taping knife under the shoe molding instead of taping the floor, brush a door's inset panels first and roll the flats after.
Instead of taping every pane, brush liquid masking over the glass — sloppy is fine, it even primes the trim it touches. Paint the trim, let everything dry, score the edges, and peel the film off in sheets.
A flapper that keeps getting replaced is the sign the seat it lands on is worn out. Water leaks past the flush valve itself, and no new flapper will seal against it.