Painstaking as the process is to assemble individual characters to form a line of words, the process of putting it all back is only marginally easier. This task can only be avoided if you have the equipment to cast type, so get used to it!
We’ll assume you have the type on the composing stone having finished printing. You’ll need to slacken the quoins; remove the furniture and chase and put these things away. You’re left with a block of type. You’ll need to separate each different face so that you don’t mix the types within each case.
In your left hand (or non-dominant hand) take as much of the type as possible: start with single lines or parts of a line and work up to multiple lines. In your right hand (or dominant hand) take as many letters as you are comfortable with. This amount will grow with practice. Your grip should be just enough to hold the type but not too firm.
Advance each character from the line of type between your folded finger and thumb. It’s best to remember what characters you hold; so you don’t have to look at them and delay the process. Note the character and find the right place in the case for it. Have this ready to drop and hover over the right compartment, release the type to drop from about 1″ — 2″. Any more might damage the type; and you should never throw type back in the case.
If you drop a letter in to the incorrect box then search for that and correct the problem before moving on to the next piece of type. type dropped on the floor or another hard surface might be damaged and so should be inspected before it is returned to the case.
Spaces can be problematic because multiple space widths might have been used. If you can tell space widths from one another then they can be distributed in the same way as letters. If you’re not yet able to distinguish between each space then reserve these on the galley to sort later on. It’s useful to place them side-down on the galley and run your finger over them to ensure they are the same sidth as each other.