I've always believed that if you have to "sell" yourself or your services then you are nothing more than a scam artist or huckster looking for a mark and a quick buck. Are you looking for a quick buck or to help someone with a quality solution to a potential problem? I prefer to help people. I believe most here are of the same frame of mind - let's make money helping people.
Now, on the other side of the coin is "education". Educate the potential customer in the differences between their 'obvious' results (which I'm sure you've already taken time to document) and how you can improve on their in-house results. If their results meet or exceed yours - why bother (they obviously have it under control)? But if they aren't meeting an acceptable standard (such as in a commercial environment) then "educate" them to the possibilities of a 'slip and fall' scenario and how you can help them avoid that situation. For home-owners, educating them about the possibility of their insurance being cancelled due to a dirty roof or a HOA warning just may persuade them (don't use it as a scare tactic). A dirty pool deck could lead to a serious slip and fall situation too as could a slimy wood deck.
Salesmen are typically trained to figure out what matters most to a potential customer and hammer that point until they get the sale.
Educating them on how you can do it faster / less expensive / better / with less potential damage /... is not sales - it's marketing. Don't "sell" your services - market them.
Know their situation before you approach them, you'll be better prepared to "educate" them as to why they need your services more than they need to do it themselves.
I will never turn my hard earned cash over to a slick used car salesman - never. I have to be convinced (i.e. educated) why I should purchase products or services.