Most of us just measure out enough beans for the shot you are pulling and keep the rest of your beans in a one-way valve bag to keep them fresh. If you measure out the amount of beans you are going to use in your portafilter basket you should be fairly close. I have a little plastic scoop and 3 of those fill my 21g basket with a little to spare.
You will always have a fair bit of c.......p in the Sunbeam, its a good little grinder but messy!!!