I iron (with very light steam) washed fabric from the back side - and iron along the grain lines - when ready to use the fabric.
If/when I find a flaw in the fabric, I put a small safety pin on the selvage nearest the problem - and a small safety pin on/over the problem.
So far, I'm not a big fan of starch/sizing. Except for things like kite-shaped pieces. I think fabric should have enough 'body' to stand on its own.