On a short hill like that, you want to be doing intervals above LT the entire way. Go at a steady pace that has your HR increasing the entire way so that you blow up at max-HR right at the top. You shouldn't have anything left to give at the top. If you do, you didn't go hard enough.

Then practice doing these intervals in different gears to work on smooth big-gear out-of-the saddle form and low-gear in-the-saddle spinning. If the limitation for you on long climbs is your legs & muscle-fatigue, practice more of the big-gear intervals. If your lungs hurt on the climbs, then do more of the spinning intervals.