Flaking from starch comes from not letting it penetrate the fabric before pressing. If you spray and then immediately iron the starch is on the surface of the fabric and when the hot iron hits it it flakes. To get the full benefit from starch you need to let it penetrate the fibers of the fabric.
I use liquid starch that comes in a large bottle and dilute it 50/50 with water. I put it in a spray bottle I got at a beauty supply place because it comes out in a fine mist. The fine mist makes the starch (or Best Press) go further and coats the fabric more evenly. Once my fabric is sprayed I roll it up and put it in a plastic bag to let it mellow. After a bit of time I then press it. No flaking or residue on my iron that way. Much the same as when we sprinkled clothes "back in the day".
I will use Best Press occasionally to freshen up a block after it is constructed but again I put it in a bottle from a beauty supply place (like Sally's) as the fine mist makes it go further.