If I was doing this, I would use Speedy entry. With the edit window open, In ms. 7 for example, treble clef, I would press "option 6"

(I'm on a Mac, Alt 6 on windows), This tells Finale that a 6 note tuplet is going to be entered. I press 4 to create 8th notes. Press 5 is you need quarter notes. Leave all of the defaults in place. Let the bracket and numbers appear. Let the solid noteheads appear.

Once you're done entering the music, with the selection tool, highlight the entire piece. Go to the Utilities menu, at the bottom select "Change". Select noteheads, select the solid notehead you want to replace, then find the notehead you want to use in it's place, click okay and they're all switched at once. Go back to the change menu, choose tuplets. Choose the new parameters (no numbers, no shape) click okay and now the tuplets should look the way you want.

This looks wordy written out, slightly confusing, but it's actually very quick to do this.

Thank you, Jeffrey. What you suggest seems very interesting, but I don't understand what "press option 6, that is Alt 6 (I am on Windows 10)" means. When I try to do that, nothing happens. I guess I am missing a step of some kind in this procedure.

… With the edit window open, In ms. 7 for example, treble clef, I would press "option 6" (I'm on a Mac, Alt 6 on windows), This tells Finale that a 6 note tuplet is going to be entered …

If I Recall Correctly, the shortcut to Speedy Entry’s Tuplet (sub-)Tool sextuplets is Ctrl-6 in Windows Finale.

In the document settings for tuplets you might like to specify that all tuplets in this document by default appear without neither Number nor Shape.

By The Way:

From the look on the screen shot it seems that there are no black noteheads at all in this document, right?

I would change the document settings:

Document menu > Document Options > Notes & Rests > Notehead Characters > Quarter/Eighth > Select…

and select the open notehead (= half note notehead) for quarters, eighths and smaller values.

Umberto,

I'm probably not explaining this method of entering tuplets very well. This is from the manual under "to enter tuplets with the Speedy entry tool".

1. Click the Speedy Entry tool  , and click the measure in question. The editing frame appears.
2. If MIDI is not being used, place the cursor on the correct pitch.  
3. Press OPTION+number in the number keypad. You can press any number between 2 and 8 to specify the tuplet value that you’re about to enter. When you do so, the number you pressed appears in the upper right corner of the editing frame, telling you that Finale is ready to group the next notes you enter as a tuplet defined by that number. If you need to enter a more complex tuplet (or want to specify a particular bracket or slur configuration), press OPTION+1, and the Tuplet Definition dialog box will appear (see Tuplet Definition dialog box).
4. Enter the notes of the tuplet. The value of the first note you enter tells Finale whether you’re entering an eighth-note tuplet, quarter-note tuplet, and so on. Finale automatically groups them and brackets them according to the default visual tuplet settings (see To predefine the appearance of tuplets, below). To enter many tuplets in a row, see To enter many notes of the same value (hands-free MIDI method).

On Windows, you would hold down the ALT key, and press the number 6.

Thank you. Your suggestions were very useful.

Umberto