Years ago I used a Leaf Valeo 17wi on an old Toyo view camera and I did have the Leaf Live View dongle. I found the focusing very hard even with the Live View. After using another photographer's Sinar P2, I bought an old Sinar P because I liked it so much over the Toyo. I still found it difficult to do the Live View focusing, with the crummy B&W live view. The Leaf Valeo 17wi was a tethered to a computer back. So this made the 'trick' I stumbled on very easy.
Since the Sinar P, P2, P3 have self locking knobs, you just let the focusing knob alone and it locks itself in position. You do not have to do the Toyo, left knob unlocks the back standard so you can use the right knob to focus and the relock the left knob, just relocking the left knob can cause some small travel on the back standard.
The trick - so I would first focus my old Sinar P first using the ground glass, slide the back over, shut the lens, do the f-stop, take an exposure. Lets say I was photographing a soda can. If my point of focus was off and the side of the can was sharper than the front label, I would just "roll the focusing knob back a tiny amount, just enough for it to move, like 1 degrees worth of a 360 degree circle" and take another exposure. Often that small 'blind' focusing adjustment would nail the focus just where I wanted it. If it was still off, do another one, either forward or back as needed. It was so simple and quick to do, takes 20 seconds, just advance the shutter, take another exposure and check the focus on the computer screen. It was so much better than opening the lens and refocusing with the ground glass or with live view. Try it.
The Sinar F is an entry level Sinar and I don't think it has self-locking focusing knobs. The Sinar C has a front F standard and a rear P standard (this standard has the self locking focusing knob, so it should work). This 'trick' works with an large format camera with self locking knobs.