I would say that 9 is fine, i started at the begining of the year and have fliers and knocking, i have found that a flier saying clean me , and put it in your window if you wan them cleaned works best, im getting around 12 per 100, but it just saves knocking and geting no custom, this way the customers you knock have alreadyu let you know they want a cleaner your just going round to sort the price, let me know how u get along, message me is you need ideas for clean me flier.
dan