I also use DuPont, the expensive stuff...and it's really getting expensive! I had to redo the hood on a 77 that I filled the exhaust hole and used Agco, but mixed some Dupont hardener in that I had left over. It worked very well.
Rexalot, 
A fairly inexpensive forced air respirator can be made by buying a gas mask and attaching an old vacume cleaner exhaust side to it. Let the vacume sit outside and fresh air is constantly pumped to the mask.
The guy that painted my Pitts airplane with acryllic paint had used one for a number of years with success. (He's still alive!)