I have a safer and faster solution to the spam can directions here. I don't know how old this recipe is, but with the pull-top cans, I'm not sure how you would remove the bottom. Certainly not with a can opener. So, here's what I did. I just washed out the can and using cheap fold-top sandwich bags, lined the can with one, opening it up and folding the edges over the edge of the can. Then, I took an empty plastic pill bottle (as tall as the can and a bit narrower) and put that in another bag. You use the two similar to a mortar and pestle, tamping the rice down into the bottom of the can with the bottom of the wrapped bottle. When it's all assembled, pull the bag out of the can, unwrap the contents and lay them on the nori. Reuse the bag to make the next one. It's probably not as fast as using an actual Musubi Maker, but there's nothing to wash up when you're done. Just throw the bags away and you can save the can and bottle for next time.
I'm so glad to see that you recommend using the Spam can as the shaper. I can't abide all the plastic "forms" sold to make simple musubi! It's easy to make with shoyu chicken as well.