Arts and Crafts Having issue with making tshirt

[branv]

I want to make a few tees for my toddler for our trip in 10 days, but last month when I tried to make a tee for his birthday I had a few issues. Was hoping someone could help me avoid this for the trip shirts?

First was that I prewashed the shirt l, being sure to not use fabric softener. It came out very wrinkled and scratchy feeling. Trying to iron out the wrinkles before doing the iron on was impossible. I must have used an irons worth of steam on that puppy! Any tips for getting the wrinkles out? Also, like I said, is so scratchy! And I thought to make the iron on last you shouldn't ever use fabric softener on the shirt? Is that true, or can I wash it like normal? Poor kiddo was twitching wearing his birthday shirt.

Third, I don't have a cameo, so I have to hand cut out the iron on. Still, with larger designs, you end up with a large piece of iron on. My problem is that per advice, I used the sheets for dark fabrics despite this being a white shirt. And the design area was so thick and unwieldy looking on his shirt. Would the sheets for white fabric be less dense/move better?

Thanks so very much!