Are you prewashing your fabric ... without any additives? That means no softener or starch or other 'stuff' such as Best Press.
The prewash is only the first step. Then iron. Yep, I use freezer paper and trim the leading edge before putting it through my printer. I do not use Best print because it will leave some extra ink. Then I iron again after the printing.
If I do by hand I do all but put through the printer. The freezer paper isn't always necessary but can be helpful.
For signature blocks I make a frame out of a manilla file folder and have a baseline drawn darkly on the inside of the folder. That way there is always adequate room for seam allowances.