Great OP, I started similar journey approx week ago. Currently have only 6 accounts but going to scale up too (already have proxies for 19 more). Well I am a little bit careful because it's my first "action" with MP, so I have joining only 2 groups per day at start.
You use "Account actions". I still did not decided if I should throw $15 at this plugin... Its worth?
Anyway GOOD LUCK!