What size of glass house are you talking about ?
Not far from me are acres of glass houses , most are of a modern construction which have built in spay lines especialy for this purpose , the older type it is a case of onto the roof and walking along with a knapsack , not sure what they use but believe it it some sort of acid, and then you gat the wooden dutch glass house construction, safest bet here would be to actualy go along under the glass open ing the dutch lights and spraying , a time consuming task. Must admit not seen any cleaned by a machine as such
Geoff