Kv, I've never heard anyone use a substance after pruning, but it's not impossible.
Why are you pruning? For shape? To keep smaller? Pruning, especially this time of year, could halt fruitng.
Dead branches should be removed though..Toni

We are pruning to tame and shape better. We cut back other trees in the yard to allow better sun to the lemon tree. We're not too worried about halting fruit production at this point. The tree is leaning to one side due to the other trees so we are trying to get it to straighten up. We have a fungus/disease/insects too. We will post pictures tomorrow.