I've used the canned spray starch and the canned sizing. Of those two I prefer the starch vs the sizing for crispness/stiffness of the fabric. Both of those, IMO, do take a few minutes to absorb into the fabric. A few years ago I switched to the sta-flo liquid in the gallon jug. Bought a $1 sprayer (as I had no others at the time at home). Mix at a 50% ratio with water into the spray bottle. I spray my yardage as I'm ironing after pre-washing. It (to me) absorbs into the fabric much quicker than the canned sprays and I can iron immediately. I have no issues with flaking or scorching with this starch. I have a steam iron with a stainless soleplate that does also not get dirty/messy/gunky with this starch.
I've not used Best Press - although a friend of mine does. Her blocks do look nice and crisp but I don't think enough better for me to have a need to switch products. Especially at the price of Best Press. Sta Flo is quite reasonable and very available.