"It was Klean Strip Odorless, and it was a very clear liquid (still is, I just checked). I mixed it in an old blender that I use for garage type stuff and it worked great. There were no chunks left after about 1.5 minutes of blending."
I used the clear clean Klean Strip but I didn't use a blender and it didn't work well. However on my second attempt using lighter fluid and again without a blender very little mixing was needed Maybe a minute with a small wood stick to get what I wanted.I also needed much less of the lighter fluid than I did with the Kleen strip.
"Maybe it was using the blender that enabled me to get it mixed well"
I would agree with that based on what I saw. Plus I didn't contaminate anything I usually use with food. Also the minimum size of Kleen Strip is more than what would typically be needed. Lighter fluid is available in very small sized which is perfect for small jobs.
" white gas is very flammable"
Yes it is but it does not make the cloth permanently flammable. Once the silicone cures and white gas has evaporated the cloth will probably be less flammable than the original untreated fabric (silicone does not burn).
"Most all of the instructions that I've found for "DIY Silnylon" or "DIY Seam Sealer" say to use odorless mineral spirits"
If you look at forums that are not related to hiking in any way they generally just say Mineral Spirits. Odorless or low VOC mineral spirits only recently appeared on store shelves mainly due to pollution regulations.

