I buy the starch at the local dollar stores. the one I'm using now is Heavy Magic Starch and it works as well as any of the others I have used before I started using the dollar store. Spray the fabric let it sit a minute and iron. I don't have much flaking at all the flaking happens whe you have the fabric wet with starch and don't let it soak in a little. When you get flakes it will come off anyway. Been using it for over 2 years without any problems. If and when the iron gets looking like the bottom needs cleaning I take an Mr. Clean white eraser get it wet put in a pan and continue running the hot iron over it til it is clean. Makes for easy and accurate cutting. Wouldn't quilt without the starch once you see the difference.
Good Luck
Suzy