TMI question about preseed?

So my SO is way older and sometimes gets soft if he’s distracted so my question is... can I give him a handjob to make him hard and put it on him? Even if it dries? Or does it have to be on him and go in wet? Cuz last time I put it on him gave him a handjob and it dried? I even put some on me... so idk... and AF showed this month so...