I wrestled with the same problem for my Maverick nose gear door. Since there is only one line going to the retract you have to be a little creative. After an hour or so I came up with the attached. It works fine. The restrictor on the relief side of the button valve is optional, it reduces the amount of air used each time the doors are cycled.

If you want to do this for two mains then just tee the two retracts together, and tee the two cylinders together. Put the button valve on the side that retacts the slowest. Another option is to use two button valves, one for each side but that's really not necessary.

Joe