Refining your search
You don’t need to type a whole filename into the buffer picker. The picker uses fuzzy filtering: every buffer whose name contains the characters you’ve typed, in that order, stays in the list, and the closest matches float to the top. A character or two is usually enough.
When more than one buffer is left, keep typing to narrow the list further, or use the arrow keys to move the highlight between the matches. Enter jumps to whichever one is highlighted.
Work through the checklist below. Load foo.txt, bar.txt, and baz.txt with :e, then open the picker and type f — only foo.txt matches. Open it again and type ba: both bar.txt and baz.txt remain, so narrow down to baz.txt before pressing Enter.