I tried a little foliar feeding once, and I used plain water to rinse off the leaves later after the leaves had absorbed the nutes and dried. I was using some liquid chemical fertilizer, the kind that leaves behind all that salty junk... so keeping the leaves clean and not allowing it to acumulate was an important thing for me to do. Doing it ensures that there's no residue or salts left behind to inhibit transpiration or light absorbtion, and possibly burn the leaves if too much builds up over time.

Of course, using that extra water to rinse off the plants will mean you gotta keep your eye on the humidity level. Also after wetting them down try to add extra airflow until they've completely dried.... I only had one big fan so I would just increase it's speed to do it. And I personally wouldn't use any kind of foliar feeding once buds have really started to develop, like around 2 weeks into 12/12.