I am a novice at anything domestic. When I used starch on my fabric I just bought the cheapest starch I could find.
I probably over-sprayed but I always ended up with some white starch spots.
I finally tried "Best Press" unscented and it works perfectly.
I also use "Retayne" and presoak my fabrics in hot water. I rinse them to get the Retayne out and then line dry in the
good months, followed by minimal dryer time to take the wrinkles out.
I'm sure there are many ways of prepping fabrics but this has worked for me so I haven't experimented further.