Spray Foam Insulation

I have a couple of bay windows that bump out from the foundation of my house. The floor of these windows was noticeably colder in winter. I made a project early on of spraying a lot of Great Stuff between the floor joists under one of the windows. I used quite a few cans of Great Stuff and it was a real pain to reach around with those little cans to get the foam everywhere. However, it made a huge difference - the floor is much warmer now. The remaining bay window bumps out significantly further from the foundation, in fact I cannot reach the end of it from the basement. It seems to me I need a more professional setup for foaming this space. I've looked around a bit. I've found a few professional spray guns for Great Stuff Pro and similar products, but since these products are aimed at pros, there is little information out there to guide me to the right setup. So, I'm wondering if anyone here has dealt with a similar issue?

Well I deal with a similar situation. I have bay windows in the living room, single pane glass and no insulation in house. That window film works pretty well but is ugly. Two of the bay windows I cover with heavy drapes in the winter. This works really well, and makes the room more cosy in the cold months.

I would need a picture to better visualize what you are trying to do; however, the great stuff pro guns are available at home depot for $30.00. YOu will need cans of foam at about $8.00 each, plus a can or two of cleaning solvent at $5.00 each. The benefit to gun foam is that you can shoot some today, close the valve tight, and shoot some two weeks from now. With the great stuff cans, you have to discharge the whole thing at once. They make a few kits, generally by tiger foam, which are good for a hundred square feet or so.