@jerzone since i completed the project i was using PEX A for, i can comment that it’s pretty straightforward and foolproof. you put the expansion ring over the pipe, use the expander tool to stretch it out, quickly insert the fitting to the shoulder designed to mark the proper depth, hold it for a while while it contracts back to its original size.

the caveat is, the stretcher tool is large and awkward, and if you have to use it in a tight space (e.g. a joist cavity) it will be tough