I lay the bike on its right side with the fixed cup in place and spread grease in the cup with my finger through the hole in the cup and then feed the 11 1/4" bearings one at a time through the hole. The grease holds them in place. Inserting the spindle locks them in. Fill the adjustable cup with grease and bearings, stand the frame up and carefully screw it in over the spindle. Using a plastic sleeve makes in easier because it holds the bearings in place while you work.

I throw away all retainers because I want my expensive French parts to last forever.