I had a love had relationship with my plough plane. I loved the simplicity and speed of the essential grooves it would make/plough. I hated that I would sometimes get bad tear out or a canted groove. Between this and the last project I think I've gotten the hang of using the tool and want to pass along my observations in case it helps someone else.
There are a few things I've learned
One hand holds the fence perpendicular and the other pushes. Yes, I am being captain obvious on this. What I've found is that the one that holds the fence perpendicular is also doing a bit more work. Let me use an analogy of sorts. When using a Western style hand plane, the hand pressures downwards change. At the beginning of the board, most of the downward pressure is knob part of the plane. During the middle of the board, knob and rear have 50 50 pressure. At the end of the cut all the pressure is on the rear. This sort of rocking of pressure helps prevent the plane from swooping on the wood. I've found with the plough plane, I am rocking the pressure fore and aft to keep it perpendicular. Initially, all the perpendicular pressure is towards the front of the plane, middle of plough pressure is in middle, at the end of the plough the perpendicular pressure is towards the rear. It's not some drastic hand changing motion but more of a rocking motion. The slight curvature in the perpendicular handle I think is designed to allow for this. By using this method, the blade moves true and doesn't go off at some slight angle and bind in the cut. That is often when I have tear out occur. In fact, whenever I start to feel some sort of atypical biding, I know that I am mechanically doing something wrong with the tool. I stop and readjust. More often than not when I don't I end up with some sort of defect in the crisp edges of the wood.
The other thing that I found helpful was putting a small wooden fence on the tool. This seemed to really help me apply perpendicular pressure.
I have found that it is the first 10 or so passes the length of the wood that seem to be the most critical. If I can get those done trouble free, I can usually get a really crisp groove. Often after the first 10 passes, I will clearly know if I ploughing against the grain. If that is the case, I will sometimes take my marking knife and deepen the channels in the wood.
Again, this is a lot of words. Mostly putting it out there to let others know if you just spend time using the tool and paying close attention, you will find little changes that make big impacts. It just takes a while to teach your hands how.
Still need to focus when using it. If I get complacent, I end up tilting the handle and chewing up an edge. I still need to spend time using are the skew rebate plane with knickers as I am still a way away from getting acceptable grooves with it. I also need to work on hand chopping mortises. Plenty of skills left to work on. I enjoy this part of developing my hand skills. Getting good at being able to do organic synthesis research was the same thing. By the end of grad school, I came out fully trained and felt confident I could make any molecule that needed to be made. I probably had about 12,000 hours at the lab bench at that point. This all ties back to the whole thing that was popular a decade or two ago stating that it seemed to take about 10,000 hours to master a skill.