Alejandro,
WHat I am saying is that if you connect the nose gear door to the same line as the nose gear, it will open, right before the gear deploys. As Terry said, you can then use a small clippard valve on the cylinder door (close side nipple), so that when the gear retracts, it hits the clippard valve, thus allowing the air to pass thru and shutting the door. This way the door only closes if the gear has retracted, and prevents it from closing prematurely or hanging up the gear leg.
Of course the main gear doors open, then close with the cyle, so they have to be on a sperate line, like you are aware.
Terry's method works well, I have used it successfully, and it is much easier to make it work than it sounds.
Tommy