We clean all the frames thoroughly first and rinse and a quick whizz over the glass, then back to the beginning glass only. Might start using virosol on first cleans now though sounds like a good idea.
I would definitely recommend charging more for a first clean, one obviously because you never know they could be just a one-off and trying their luck, happened a few times to me when I was starting up.
Also its psychological, charge more and sell the reasons why, I say to them that we will effectively be cleaning them 3 times the first time round and they will really notice the difference. And also when you quote a first clean price and then a reduced price for regular cleans the last thing they hear is a lower price, and a 'discounted' price - so they will have forgotten 'how much?!' for the first clean because they think they have got a deal. Use the words 'discounted price for regular cleans thereafter' and everyone is happy.