Measure across the first section of the counter edge. Transfer the measurement to a piece of trim, with two marks along the top of the trim and the measured distance between them.
Set the trim on your miter saw, standing on its bottom edge so it’s in the same position it will be against the edge of the countertop. Slide the trim to put one of the two marks under the blade.
Swivel the blade to the correct direction and angle for that end of the counter section. If the trim is ending at an outside corner, swivel the blade 45 degrees out, away from the piece. If it’s going to an inside corner, swivel the blade 45 degrees inward. If it’s terminating against a wall, swivel the blade so it’s straight across at 90 degrees. Make the cut.
Move the trim so the second pencil mark is under the blade. Turn the blade to the correct angle as before. Cut it.
Set the trim against the edge of the counter, so it covers the exposed edges of the tile and the wood edge of the counter. Secure it with your trim nailer, shooting nails through the face every 12 inches along the top and bottom edges.
Repeat for each section of the counter perimeter, butting the mitered cuts of the trim against each other.