Two hours sounds awfully long for a somewhat delicate surface treatment. Ideally, as I mentioned before, generally turned inside out, low temp, tumble dry low or air dry and DO NOT iron over the foil if pressing of garment is needed. I use a laundry bag to help reduce friction, which can rub the foil off. You want to use your machines equivalent to a delicate hand wash. You do need to mollycoddle it a bit. It's also more permanent with the heat set adhesive rather than a rub on glue in my experience. I was using the adhesive designed for commercial silk screen production either painted, screened or stamped on.
The powder is awesome but tricky. It's by Bo-Nash and they do have many videos. It's used by cleaners for garment repair apparently. Anyway, anywhere you get a speck of the powder the foil will adhere. They suggest using a stencil then placing a silicone ironing sheet over it, press then carefully remove the stencil. It's wonderful if you want to do a Fairy dusting of powder then lay the foil over and press. Nice in mixed media applications.
It might end up being too fiddly for practical use on a small childs garments. Pitty.