Painting a straight line on inside corners of windows

I am going to be painting on the exterior side of several dozen windows.

The wall is made of stucco concrete blocks, and the window is recessed about 4" into the wall.  It is this recess I need to paint.

The window is white and aluminum.  The wall is gray.  The inside corners are sealed and caulked.  A coat of white primer has already been applied to the masonry wall, now I need to paint the 4" recess in gray with a nice straight line along the inside corners.

What is the best way?

(1) Use a cutting brush and do it slowly.

(2) Put tape on the aluminum window frames and paint up to the tape.  I have tried this in the past and most times the paint bleeds under the tape.

(3) Use one of those special straight line trim gadgets.  Like:

or

or

or

or

or something else.  Do any of these work and don't smear and bleed into the adjacent wall?