Try it first without a load and don't blame me if things go sidewise. As I said it never feels safe (probably isn't) but if done correctly works,
There are two lifting dogs that index on the gear rack. Each dog has a little post on it that you can use to pull it in and out. To lower the jack one tooth on the rack you:
1. Disengage the lower dog from the rack and raise it one tooth so that it is engaged with the tooth directly below the upper dog. This does not move the load or the rack, only repositions the dog.
2. You then push down on the handle which lifts the load using the lower dog and unweights the upper dog.
3. Disengage the upper dog from the tooth it is in and lower the load with the handle.
4. As soon as the next tooth clears the upper dog, release the dog and let it catch on the next tooth, taking the weight of the load and unloading the lower dog.
Repeat.
I should state that the dogs and rack should be clean and well greased so that the dogs move easily and that you should be well within the load limits of the jack as you have to lift and lower the load with one hand while working the dogs.
Teryk