I just needed PCB quickly and ended using same method. worked like charm.

I ironed for 2 min (counted in my head) on high, without pressing too hard or moving (ok I moved at the end just see paper color change as indication it is about done). i just used hot water to soak and let it cool down (took about 5-6min) then washed it with cold water and peeled bulk of paper. getting last bit of paper took another few minutes until I tried eraser to help peeling it off. didn’t need any patching with pencil, entire print was perfect. just for test i did place small mark at the edge using sharpie permanent marker but that wasn’t good enough, about 50% was etched through and looked weak.