I would use a clear length of plastic pipe. Fire the bike up and put your thumb over the end of the pipe to feel if there is any pressure there.
Also you can see if oil. if any, is being blowen out the breather.
I have breather pipes on the rocker caps of my pre-unit Triton, which go into a small plastic bottle cable tied to the frame near the back of the engine.
I have never had to empty bottle.