Hello! I've been using jake for about a month I think, and without question the easiest way is to open a pouch is with a siccor and cut it like I show here (the green line) and not as adviced from the pouch (the red line). By making the hole smaller it is easier to pour it in the shaker, and also it will not come out all at once in a dramatic fast way..With practice you can "easy" make this kind of cut without any siccor Before cutting it make sure to hit the pouch with your fnger where I made the red line a few times to avoid spill when cutting it.
Also I recommend to pour in a 3rd of it at a time or halv of it if it's jake light, and after pouring just lightly shake the pouch over the sink to get those little annoying powder in the sink instead of on your table when you put down the pouch to shake the shaker!
When it comes to cleaning I'm always using the shaker at home so I manually clean it with a brush directly after each use.