I had tried Chagrin method for finding the force but I don't know how to really judge that but it wasn't easy to move.
You could use a spring balance, as used for weighing fish, to measure the force.
There will be an initial force to get the thing moving then a lesser force to keep it going.
In theory if the TV were mounted on a good bearing then the weight of the TV is irrelevant as it acts vertically through the bearing. The force you are applying is just to overcome the friction.