radman:
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.
There are also some fairly inexpensive digital hook scales, many advertised for weighing luggage. I have this one and found it to be decently accurate (especially for the ~$10.00 price) and probably precise enough for this type of measurement in either the grams or ounces modes (it also has kilograms and pounds modes). However, it's really basic without features beyond the four measurement modes; i.e. no ability to store and recall values, retain the highest value, etc...