+1 trigger/button valve is the way to go for doors that dont require some kind of closing once gear is down. I use this setup on canopy lock function and seriously considering adding it to my gear doors. I can drop down to just a UP-6 valve for brakes and nothing else. saves lots of money and some weight. [:-]
ORIGINAL: KC36330
if it's as simple as doors open, gear out.........gear in, doors closed (F-16 as an example), you don't need a sequencer or a fancy radio with delay, a trigger valve on one of the gear legs works great.