Hello!
I've made some patches by myself
I screenprinted my patches,then cut a shape,
Iron the form-flex on,so it's not so thin,
iron the form flex under the shirt-so it doesn't wrinkles while sewing,
put some adhesive spray on the patch-so it stays in one place on the shirt,
and sew it on with thick zig-zag stitch with regular sewing machines.
Looks good-but too much work...
And it took me some time to find form-flex-I even posted a question about it:
Pellon that looks like a regular fabric
And they have this adhesive material in Jo-ann store,i don't remember the name-that has glue on both sides.I don't now how long it holds the patches...