For the double basket ijn my VBM about 18g is what I have been using but it looks as though 19 or 20g is better. I used to use a scale but now I find a level 1/4 cup measuring cup provides exactly the right dose.
I dont fuss that much about step 1 as there will be no foreign objects in there. Does your hopper have a gate? I find this almost essential for per-dose use.
1. Hit the dosing lever a few times to sweep any old grounds out of the doser into the doser lid
2. Add required dose of beans to the hopper with gate closed
3. Turn on the grinder
4. Open gate and ensure all bean to fall into the grinding chamber
5. Start dosing straight into the portafilter after a couple of seconds.
6. When grinding stops, I turn off the grinder and *sweep grounds out of the grinding chamber chute (that feeds into the doser chamber) using a brush. Then I turn the grinder back on so any grinds left in teh throat are ejected into the dosing chamber and then dose into the pf
Step 6 may not be necessary for the SJ but the Mini always clumps here.