I would like to set up a flag painting station at a festival. I have a bunch of white pillowcases. What kind of paint/painting devices should I use? Ideally, the paint would allow rapid application (pens are pretty slow if you're covering a whole pillowcase with a simple design) and dry quickly (traditional fabric paint doesn't), although I suspect those may be mutually-exclusive requirements? It doesn't need to look good up close and it doesn't need to be durable.
Rollers in various widths with a fast drying acrylic.
I would insert a piece of card inside each pillow to stop the design running through to the other side and to keep the fabric straight. Your challenge is to keep the fabric flat.
To speed the drying process, or to store or display finished or unclaimed works, rather than using a table, find some sort of rack arrangement, or use the sides of the marquee with bulldog clips.
A hair dryer will speed up the drying process.