The short answer is probably one you don't want to hear. I'd try to find a quality shop to rebuild the trans. While just rebuilding a 46RE isn't that hard using a good reference manual, going into one that others have had their mittens into can open a can of worms. There have been several issues with these transmissions, like overdrive coolant flow, that there have been several methods of "fixing", and some don't play well with others. There are also several variations of "shift kits" that may or may not work with each other, not to mention some clash with the electronic governor function in the valve body. To be honest, even though I am reasonably familiar with these units, I would probably pull it apart, and if I didn't find a glaring error in assembly, I'd probably source another complete core to rebuild, or at least a valve body.
That said, it would also be hard to try to walk someone through all the things that could cause your issues, since they appear in 2 different gears. Different apply circuits, different mechanical parts used. And to properly diagnose sometimes requires monitoring pressure circuits with gauges, and electric solenoid apply circuits with a scanner.
If your research has made references to people curing shift issues with changing solenoids, they are usually referring to changing the governor transducer and pressure solenoid. This fix is more for erratic shift speeds and not a slipping issue. They take the place of the mechanical governor in the RH style, and they read and adjust governor pressure using input and output from the computer. There are HD versions of these - most diesel transmission sites sell them. One actually adapts an Allison solenoid to the Dodge trans.
This probably isn't the answer you were wanting to hear, but I hope it explains what you are up against.