And I've successfully invoked the plugin by poking the address into the browser, so I know that works.
The address for the plugin is not the way it would look on the web. You are not really 'talking' to your site like you would be when using a browser from somewhere in the world. You are talking to the servers at your hosting service, so the "path" is lightly different.
Here's the actual "path" I used in my example above: /
home3/
my-account-name/public_html/mid-southweather.com/
You should be able to see the exact text to use in cPanel if you look at the "Files Manager" section. The beginning of the files 'tree' will have the first two parts of the "path" (/
home3/
my-account-name). Generally, the next piece is
/public_html/ Lastly, the domain name for your site. Then, you'd put the name of the file/plugin that your already know. It might be easier to simply write it out in TextEdit in one continuous line and then paste it into the text box in the cPanel CRON page (my host doesn't have a very large text box, you can't see the whole 'command' in there). After you click the "Add..." button (whatever it's called) you usually can then see the full command at the bottom of the page.
BTW, I use the same "typing" method as you described: "poking"! Usually with one finger per hand!