Turn down all the levels of detail and number of branches. Starting with the trunk adjust one or two variables and create the tree, see what you get erase and repeat. When you get the trunk the way you like move one to the next level. Once you get the feel for what each setting does its pretty fast. Its tempting to make allot of adjustments at once but you cant really learn what each variable does. Please share you’re results I like 3d trees.
Just read the documentation for Arbaro. Gen3 is just a reimplementation of Arbaro using Python. You could even build the tree in Arbaro, which might be a little easier since Arbaro has diagrams showing what each control does. You can then save the XML file and open it with gen3.