Hi Jim,
Having both the Stationary Pad for adding info to a batch of images, and the IPTC Info dialog for adding to individual images is brilliant. In fact with many aspects of Photo Mechanic you'll find there are multiple ways of doing the same job depending on the circumstances and your own personal preferences. I've used PM for over 15 years and it has become indispensable for me, and that flexibility is a big part of it.
As you get to know the program you'll probably find you use both the Stationary Pad and the IPTC Info dialog regularly. My typical workflow is to add most of the info using the Stationary Pad during ingest, such as photographer name, copyright info, city, province, country, event etc. (basically any info that is common to all the images I'm ingesting). That means 75% of it is done before I even look at my images. Then when I'm done culling out the garbage, I'll go through the keepers and finish adding the rest of the info, usually Keywords like people's names for example. Lets say there are 20 photos of John, 20 photos of Paul, plus a few photos of other random people. I'll again use the Stationary Pad to add John and Paul's names, as it is faster to batch 20 photos at a time. For the other random people I'll switch to the IPTC Info panel and add those names one at a time. If there are a few images needing the same info you can use the copy/paste buttons inside the IPTC Info panel to copy all info from one image to another very quickly.
Here's another hint. Often times I'll shoot an event with a group people, let's say John, Paul, George, & Ringo. Some images have all 4 people, some have John, Paul & Ringo, some have just Paul & George, etc. It's a real pain when there are so many combinations, but rather than enter the names into each photo one at a time, you can kinda batch those too. I'll add all 4 names to the all the images using the Stationary Pad, then browse through each image using the IPTC Info dialog and just manually delete the name of anyone not in the photo. It saves me lots of typing time. You could do basically the same thing with the copy/paste buttons in the IPTC Info dialog too. Having both the Stationary Pad and the IPTC Info dialog at your disposal allows you to come up with all sorts of time-saving techniques to suit your needs.
I'd also highly recommend learning all about Variables. They are extremely handy for IPTC tasks, for file naming & renaming, and more. When I first figured out what I could do with variables my head nearly exploded... a very powerful tool.
Good luck!
Gord