Begin your painting project by pouring thoroughly mixed paint into a bucket and dipping a quality 2"-2½" wide nylon/polyester brush into the paint.
With your brush, begin painting the inside frame of the window starting at the top.
Continue until the inside frame is complete. Let it dry.
Raise the lower sash and drop the upper sash.
With your brush, paint the upper sash beginning with the crossbar.
Continue to the lower sash beginning with the crossbar. Repeat the process with the obstructed sash areas.
Paint the window casing and sills. Let them dry.
Starting at a top corner of the window trim, paint the side edge of the trim where it meets the wall. Continue until all side edges of the trim are complete.
Reload the brush when necessary to maintain a wet edge.
Return to the top of the window trim and begin painting the face of the trim.
Continue until the window trim is complete.