"In general, the answer is that on the English (and duets) the air valve is not used during playing. "Signor" Jame Alsepti introduced and (with Richard Ballinger) patented a system of paired air valves -- one in each hand, and each working in only one direction of the bellows, -- and he apparently promoted or taught a style of playing using those valves while playing. I understand that Harry Boyd commissioned instruments with such "bowing valves" from both Wheatstone and Lachenal, and the existence of a few such instruments has been reported here on C.net over the last couple of years.
But there don't seem to be any contemporary players who have bowing valves that actually use them while playing, and I don't think it's even clear how Harry Boyd used them or whether any other performers ever did. There doesn't seem to be any need for or even benefit from them while playing an English. The idea that such "bowing valves" would be helpful in using the bellows to imitate the bowing patterns of a violin appears spurious, since the violin has no corresponding aids, and so any pattern of reversals -- bellows or bow -- that would exceed the limits of the bellows should be expected to go beyond the end of a bow, as well.
Standard (one hand, good for both directions of the bellows) air valves seem to be used -- and useful -- only for the purpose of opening or closing the bellows without playing a note."
Dick: The above paragraphs written by Jim Lucas in March 2006 may be helpful. Do your two valves work on both the push and pull or are they "one way' only? An interesting instrument indeed.
Best regards,
Gerry