The Hispano Buchon had a constant speed prop, it did not have manual control like some models of the Me-109. The pitch was changed automatically through the pilot's throttle movements.
Correct bpk1234. The Buchon was fitted with Hamilton Standard propeller as far as I know. It was only the early models of Bf 109s that had manually adjustable propeller pitch; pilots flying the earliest Emils in combat learned they had to grow an additional appendage to operate the propeller pitch lever that was placed rather inconveniently on the instrument panel.
Actually, prop pitch is controlled by a propeller governor, which maintains a constant engine/prop RPM by varying propeller pitch to match prop rotary resistance to engine torque at the RPM selected by the cockpit prop control lever. This makes life a lot easier for a pilot engaged in aerobatics or Air Combat Maneuvering, as it relieves him/her from constantly monitoring the tachometer to keep the engine within RPM limits during aggressive maneuvering. Eyes on your opponent, not in your cockpit.
Cheers,
Wes