Maybe this will help - if you need more info from the manual, let me know.
The instructions explain how to do it with one hand . . . BTW - notice that they say to reach under the table, not put your fingers through the trap door -that's only to see what you are doing. I use both fingers of both hands through the trap door. Guess I'm doing it wrong LOL!!
Got on my photobucket site and realized I already had several pictures.
This is the Slim (older)
and Stout (newer)
And the two bobbin cases,
Stout and Slim
