Once you have your store set up you need to get some pieces to inventory. Everyone has a different way to sort. I have changed the way I sort many times. When you get a large lot of parts like this to sort it can be daunting.
I sort according to Bricklink’s categories since it is how I have to list the pieces. I usually start with a few of the big categories first. Bricks, Plates, Slopes, Tiles and Wedges. I have this checklist on the totes that I store pieces in. When I sort out the categories I check it off with a dry erase marker so I know what has been done in that tote.
I will go through a box of parts and pull out all the pieces that fit in those categories. No matter what the size or color. This is after I have sorted out the Bionicle parts and now are grouped into categories.
I have two Ikea kitchen cabinets with six drawers each. The boxes are from Ikea as well. When it is time sort down to the part level I sort into this boxes. You can use anything but I like that I can keep the parts in the drawer and shut it when I am done. At least with these pieces I try to keep each box a different piece but will put some together to save space. For the Animal categories I put them all together.
When those bins are too full I will either bag them up to inventory later or I will take a bin and sort it out by color. At this time I will check the condition. If it is too scratched, has bite marks or discolored the piece is discarded
I use trays from the Master Builder Academy sets. I got a lot from a seller on Bricklink some years ago. I use zip bags as well. Other sellers use cups or make a custom sorting tray. Find whatever works for you and works for your sorting area. Now it is time to enter the pieces into my store.
The only thing that I never do is sort by color. It is harder to sort the pieces out when they are all the same color. I have always tried to find more efficient ways to sort the used bulk pieces. So far this is the best way that I have came up with to sort.