Yep, clean the canopy with dishsoap or the like and dry really well. Then, sray window cleaner on the side you are working on and put the decal on then slide it where you want it, smooth out the bubbles and let it dry.
Your on the right track but you can use just about anything that will stay wet for a little while and then dry on it's own. I think it is the alcohol in the window cleaner that causes it to dry. you can use a napkin or paper towel to blot it dry also.
The trick is to get a liquid that will give you enough time to "work" the decal into position. Then you can squeegee the bubbles and wrinkles out of the decal before it dries.
Makes it a lot easier than putting them on dry. Don't be afraid to soak the canopy while working it. I had to do it several times as I tried to remove the decal from the sheet.
Hope this helps and good luck on the decal placement.