I starch all the time with 50 starch/50 water put in a sprayer. I have a plastic dishpan that I used to control the over spray by putting my fabric in it to spray one side, turn it over etc. I then roll my damp fabric and put in a plastic bag and wait for the fabric to absorb the starch and then press. I use a piece of muslin over the ironing surface and then just either throw it in the washer when it gets too stiff and dirty or throw it away and use another piece.
I live in Florida where humidity and bugs are a given. I never have had problems with bugs in starched things and I store all sorts of starched scraps.