I use earth friendly spray starch non-aerosol fabric treatment from Lakeland. I have found that it is possible to water down which helps with the cost.
I only spray lightly on fabric when I will be handing a lot usually applique. I may spray at end of making blocks.
New tip........ When you have sprayed a friend wraps her blocks in kitchen foil. They are always lovely flat and never creased. Her daughter does the same. Perfection.