We use cheap bathroom scales, they seem accurate to within a couple of kilos which is fine, typically we run at +/-90kgs and have a hitch and towbar permissable of 120kgs, so a few kgs makes little difference. (Most noseweight gauges only go up to 100kgs).
Using them is simplicity itself, I just raise the jockey wheel, letting the steadies take the weight, put the scales under the wheel and raise until the steadies are just off the ground. I've not found a few inches of hitch height makes any difference.
The steadies are perfectly capable of taking the caravan noseweight, about 45kgs each steady.