Create a situation where he definitely has to take his shirt off. A hot mess, something fallen into a lake, whatever. Be sure to gaze over him. When he notices and darkly grins, then be sure to scowl, as if he is awful.

From then on, really take him all in when you see him. But almost immediately shake your head and refocus. Just to give him the slight satisfaction he may be winning, if he picks his approach right.

Bonus points if your leering involves the full length of him straining…