a quick a accurate way to determined the tongue weight, take the towing capacity, is 10% of the trailer and load weight and you have it. Form my big 3/4 ton burb it has a 1000# tongue weight. So I have a #10,000 cap. trailer (1000#) and 4Runner at say 5000#, my tongue weight would be 600lbs, well with in the 1000lb max.
One can also use a weight distributer to reflect some tongue weight back to the trailer, just keep and eye on the weights, be informed, never speed, and always remeber the trailer is back there.