I use one for our tub refinishing business and here's what we found works well.
From top to bottom, start with your company name.
Below that, a graphic of what you do.
Below that.. the statement "we just powerwashed the home at (and then a blank line for filling in the addess) and it looks beautiful".
On the bottom, have your phone number and possibly a code for a discount when calling for scheduling.
This will help you track them to see how effective they are.
We always to what we call the "street 10". We do two homes on each side of the home we worked in, and 6 across the street. If you have time, you can canvass the entire neighborhood. With powerwashing, you may want to do more homes since people can drive/walk by and see your work.
We have gone months without a single lead from our canvassing, and then all of a sudden, every call is from the door hangers.
Keep it simple, to the point, and they will work.