It's a bit late to add, but I've found that the dry ice is much less effective in summer. When it's nice and cold outside, the dry ice works wonders. I started when it was about 40 deg outside and pulled the entire floor of my Nissan out in 30 min and about 6 pcs. I got busy with life and came back about May to finish the rest of the car. OMFG I couldn't get anything to come loose!
Finally I wound up packing towels under the bottom of the sheet metal, and then put the dry ice down on top and covered it in more towels. that finally did the trick and got it cold enough the glue finally froze.