You appear to be confusing the process of sorting records--ordering the current found set into a specified order and finding records--pulling up a found set of records matching specified criteria.
To find all records where a given field is empty, do this:
Enter Find mode (click find button in status area)
Enter a lone * in the field
Perform the find (click perform find button in status area)
This can also be scripted.
To find records where a given field is empty, use = instead of the * operator.
To find records where either field 1 or field 2 is empty:
Enter find mode
Put = into field 1
Select New Request from the Requests menu
Put = into field 2
Perform the find
To find records where the field is empty in one of 8 fields, you'd use this last method, but create new find requests so that you can put the = operator in to the 8 fields--each on a different find request before performing the find.
thank you so much!