Use Replace Field Contents from the Records menu to alter the value in a field for every record in your found set. SInce this cannot be undone, it's a good idea to make a backup copy of your file before you try using this batch update tool.
That menu option is only accessible if you have the field you want to replace selected. Not clear how I select multiple fields.
Clicking on the Field Name, for example (I'm using the table/spreadsheet view), doesn't select that field for all rows. Looks like I can only select one field at a time, which doesn't allow for the bulk edit I'm looking for.
The "Replace Field Contents" affects all rows in the found set, even though you click one field in one row. The one field you click in will be the thing to change in all rows. It doesn't matter which row you select, as long as you select the correct field in that row. Then the"Replace Field Contents" will do that bulk editing.
The headers/field name in table/spreadsheet view does not act the same way as it does in Excel.
(Which can be a pain when it's not wanted, because people do that all the time, and there could be 500,000 records/rows that are changed at once.)