The couplers are "supposed" to couple by simply backing into the car(s). However, due to friction in the coupler latching, you frequently have to "bash" them to get them to couple. That's why I mentioned smoothing the internal surfaces.
You can't really time the coupler button push to easy the coupling unless you're very good with your reaction time. The coupler is only energized about 1/4 sec for each button push.
