I can consistently switch between Ortho and my laptop, hitting nearly 70WPM on both. I would say it took about a month before something clicked in my brain and I stopped trying to use my thumbs for mods on my laptop and miss hitting the key locations. Just give it more time. Your muscles can remember a ton of different things, brain just needs to figure out how to organize it.
I am not sure exactly how that kit goes together, but you can really use anything non conductive. If you take the back plate off you can use a vinyl sticker/tape of any kind. Once you put the back case back on it would do a nice job form fitting and staying even after the tape loses its stick.