It took about 110 cans to do this. I actually used 120 but because the cans were stored cold, a lot had some left which I couldn't get out, so probably lost a load.
I usually do at the beginning. Sit there neck deep for a while, feeling the grasp of the foam holding you tight. Usually my initial submergence is a slow one so I can feel the foam creeping around my head and over my face. Once you're totally covered you don't get that anymore.
I hope you do manage to do some. I want to do some more but I have to plan when I do them carefully. Mainly due to the clean-up time, but I also don't want it so that I'm in and out. I think I spent about an hour wallowing in this lot, and believe it or not I put a fur coat on and submerged in that too. No photos as yet though.