I tried these sites and I wasn’t able to get into any of them.
We have had 3 people out. One recommended injection and ground drench.
The second recommended 2 ground drenches.
The third recommended one injection which would last two years.

Can you tell me which is preferred or if any are effective?

Joe,

As a certified arborist I can tell you all the methods work. Different people have different reasons for using one or the other. Using the soil injection kills some beneficial organismss such as nematodes and protozoa. Some people would rather not kill benefiicals of any kind so they prefer not to use this method. It can take up to two weeks for the material to be taken up by this method. Some people don’t like the direct trunk injection method because you are wounding the tree(albeit, a very small wound)by either drilling a hole to insert the tube or inserting a plastic stopper. Plus doing it every year or two produces a series of wounds that can end up girdling the tree. The direct injection gets into the tree quicker. Timing is important in both cases.
I recommend you find a certified arborist who has been doing the treatment successfully via a method you/they do not have objections with. Prevention is the key. Even though you can still treat a tree that has the borer in it,(they did it very successfully in Michigan) the insect damage disrupts the vascular system and makes it harder for the material to be taken up.