If you've managed to get a Braine gear working properly first go, well done. In fact, very well done. Normally its a fact of life that a boat so equipped will only sail straight and true when it will give you the longest possible walk, or if its breezy, run, because it "knows" that you have to go 400 yards for every 100 it does.
Usually the rudder on a self steering boat is intended as a trim tab to keep the boat sailing straight, rather than steering. Having said that, many sail their yachts with steering only. There is a body of guys at Fleetwood who insist on it as a local class rule, usually involving multi masted boats using redundant racing hulls.
It might be a good idea to start with the sails let out to about 25-35 degrees as a starting point. Like that, you should be able to perform all the usual manoeuvres reasonably.