I use Best Press and iron before cutting. I don't pre-wash. Once in a while during the piecing process I'll use an extra shot of Best Press on seam intersections if they don't want to lay flat. I buy Best Press from JoAnn's with a 50% off coupon and that makes it pretty reasonable.

I love Best Press and that is what I use if I have it, if I don't I use starch. Makes the blocks so nice.

I use my vodka mixture before cutting, during pieceing, and on the finished block before stacking on the others. That way when I Am finished sewing my blocks together all I have to press are the seams and it's ready for the LA to quilt. I use an old Best Press bottle as it has a fine mist. I love my own mix as I can add any scent that appeals to me when I mix it up. lol

I may or may not prewash, but I use Niagra non-areosol spray starch most of the time. I have also used best press and sizing -- like the sizing least -- but the Niagra is cheaper. I have also used Best Press, but it is so expensive.

I prewash everything, fold smooth for storage, and iron before cutting. I never, ever use starch, sizing, Best Press or other 'stiffeners'. I prefer fabric 'au natural'. I have, however, been known to mix my vodka with cranberry juice and apply internally from time to time.

i am a sometimes pre-wash- sometimes not-
i generally have a can of niagra spray starch on the end of my ironing board, along with a can of sizing-and a spray bottle of water.
when i am sewing if i have a fabric which has wrinkles i spritz with water (i never put water in my iron-i don't like the spatters/spit/leaking) if i am cutting and my fabric is moving around- starch will generally make it crisp enough to make cutting more precise- i also use starch sometimes when pressing a (complicated) block which needs nice sharp edges/points-
sizing adds some body to a fabric without the stiffness of starch.
i do not use best press or any other product with perfumes i do not want to add some STINK to my fabrics- especially if i pre-washed to get rid of unpleasant odors- i make quilts for lots of people- some have allergies- i don't want to be responsible for causing anyone respitory distress- so no perfumed products are used on my fabrics- and to me the stench of best press is about the worst available. i know some people love it- i'm not one of them- and i participated in a swap once where someone sent me a block saturated in the stuff---when i opened the package in the house it caused an almost immediate reaction for my poor hubby- we had to go to the hospital/emergency room- for breathing treatments- spent 7 hours in hospital- and i had to get home- remove the horrible block- and clean-air-clean- run fans (in the winter time) with windows open- to get the offensive odor out of the house before he could come back home.
so, unless you only make items for yourself- i never recommend adding perfumed additives to your fabrics...you never know who you may send to the hospital.