Heya,
If you try to hold the camera like you would handheld you will basically add the weight and leverage of the monopod onto your arms and it will be as if you were holding something bigger/heavier.
When using a monopod, you use the monopod as the base. Long lens technique still applies (ie, I hold the top of my lens, pushing down onto the monopod). Or you can hold the monopod or base of the lens collar, and push down. The hand sling is also useful for pushing down. This creates a firm contact with the ground and then it acts more like a tripod at least in the vertical plane. I also sometimes brace the foot into the inside of my foot/shoe so it doesn't scoot around if I'm pushing on something that slides, like sand. From there, the camera becomes weightless, and you simply control it in the horizonal plane.
Monopods are really for providing vertical stability and take the weight off your arms. Without having to hold up the weight, you can use yourself to stabilize the horizonal plane better because it requires no muscle effort. Let the monopod take the weight and push it into the ground in terms of where you apply force.
I use a tilt head on mine so that I can angle up/down without having to lean with the monopod pushing at an angle so that it's always a downward vertical force when I apply it.
With this, I'm able to get down to 1/40s~1/60s shutter speeds, no problem, with even 600mm.
Very best,