I have to chime in here, I have been teaching machine embroidery and quilting for several years now and this is what I always tell my students. Cheap starch is your best friend, yes it will flake and yes it can get on your iron and on your machine feet. The best solutions to this is:
1. Use several light layers of starch, never heavy spray.
2. If you have an expensive iron, go buy a cheap iron for starching. There isn't a law that says we can only own 1 iron.
3. If you are starching for a dense machine embroidery design, get it as stiff as possible, you want it so that it looks like it would break if bent. Think cardboard.
4. If you are starching for quilting, think paper. Smooth and flat.
5. Save your Mary Ellen starch for finished projects, it is more of a sizing and will never make your fabric stiff.
6. Be cafeful with scented starches, some can be very strong and cause allergic reactions. I've had students complain about it causing headaches.
7. You can re-starch anytime you need to as long as you haven't marked your fabric with any type of pen including wash-away or air-away. Ironing them can make them permanant.
8. Clean your machine feet with alcohol pads.
Hope this helps answer some of the starch questions. BTW I always starch my seams, not only does this make them marry better, they stay flat and you won't get as many turned seams when you cross sew from the other direction.
Hugs, Gail