2-3, 1, 0, 1-2, 2, 1, 0, 2-3 then reverse for one octave. for two octave keep going starting with 1 (the second fingering from the left)
Fb would be the same as E natural, so it would be open.
Ok Hi I play the french horn so I know Just Follow these Easy steps and learn Keys Will be marked 1,2 and 3 from Top to bottom Ok here we Go! Remember to change your Embocure as you Go( Your Mouth...
C major scale. C-open.D-2.E-open.F-1.G-open.A-trigger 12.B trigger 5. C-trigger open.
If on an F horn, you finger D flat with the first and second valves.