Tim,
Got a couple questions that will affect how I answer your questions.
What is the action involving the pillow? Does it get waived around? Or...Does it just lie in place on the bed or sofa or where-ever? How is it dealt with before the "
gag", tossed around,
lay in place without being moved or touched, hits an actor over the head,
etc.? How is it dealt with
after the "
gag"? If there is a lot of action before and/or after, can the pillow be secretly switched out?
Second, is there a licensed
pyro person in your area that you can work with to obtain and properly use
pyro products? The reason I ask is that some of the best products are available right there in California, but will only be sold to a licensed
Pyro Tech. I'm certain there is someone in the San Francisco area, you just have to find them.
That said, the Theatrefx products are a good product and a strong possibility for your
effect. Another possibility is AB
smoke. There are many sources, here is one:
http://www.rogergeorge.com/special-effects/expendables/a-b-smoke
Also, as mentioned before, virtually all the candidates for this
gag will indeed activate particulate
smoke detectors if proximity and/or volume is sufficient.