For really small items such as bolts I like draws with the name of the bolt say M6 and a sample on the front and running the draws of each item down smallest to largest size so M$ down to M8 so volunteers get a fell after a while for the size they need. For larger parts such as brake blocks I like to see all the brake stuff or gear stuff together. We use the kind of removable boxes that clip on to a wall bracket with the name of the item on the box and on the wall where it goes. The advantage of these is that you can see in to the boxes when standing back and you can remove the box to sort item. I think if you have too many items to fit in a draw you need to cull the stuff in the worst condition or it just makes finding the good stuff harder. We get volunteers to do this with the more experienced helping the newer as a way of learning about the relative value of parts.
Geoff Smart Back2Bikes Port Melbourne