When I stated in April 09 I sent a letter to all local estate agents offering this and window/gutter cleaning to smarten properties up in order to help get a sale / let. Didn't get one reply. Followed it up with phone calls. No interest at all.
At the same time I was knocking doors. By 3 months in I had a round of 200-ish plus. Wore out a pair of boots and my knuckles were bleeding from all the knocking but haven't knocked a door since.
Burn some boot leather is my advice.