The Massey Plugins Wet/Dry plug-in is an older Massey plug-in that was part of the Massey Tools free bundle of plug-ins. These were some of the earliest Massey Plugs and I believe you can still get them out there, although I don't remember now what formats it comes in. I don't recall having problems getting this and the other plug-ins in the Massey Tools bundle up and running and it has run smoothly for me ever since. The make up of the plug-in couldn't be simpler. Basically you put this plug-in around another plug-in to controls it's wet/dry signal. This can be useful for plug-ins that might not have this control built in like many plug-ins will. Either way, it can serve as an extra control for this when needed. All the plug-in consists of is a wet/dry knob and a predelay knob. I don't think a manual was ever made for this, nor would one be necessary.
I'm currently running the Massey Plugins Wet/Dry plug on my home system, but I've used it on others as well. My computer is a Mac Book Pro that has a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM. I run the plug-in in Pro Tools 9 that I use with a Black Lion Audio modded Digi 002R. This plug-in takes up virtually no processing power and I can't imagine it not running smoothly on a stable system.
Massey Plugins' Wet/Dry tool is one that would be useful for any DAW user. The entire Massey Tools bundle is a great thing to have as it's got a couple of great plug-ins that are simple yet great to have. This one is quite useful for getting creative with your plug-ins. It's free so there's really no excuse! I'd get your hands on the whole Massey Tools bundle today if you don't already have it.