You can freelance greet. I've done this in the past. Not just as an IC professional on an old character, but also as a gang member before that.
A good way to justify greeting for yourself without an official job-oriented automated payout is to seek ways you can turn greets into profit for yourself. A good first step is to look at the things you use to make money for yourself and then cut immies in as middle-peeps. There is a fairly easy to access automated trading system (that I figure nearly all, if not every player uses at some point in their gaming experience) that (in the case the immie is a new player) gives a taste of that entry-level auto income system, gets them RPing and puts flash in their (and your) pocket.
Moreso, there are also ways to make money off of immies (and greets in particular - think about first mover advantage) without using auto systems. Think about everything as a commodity. EVERYTHING. See if you can come up with some common things you gain from every greet then commodify them and find buyers.
As far as learning about greeting in general, I'm torn between saying "it would be nice if anyone interested could have free access to that info" and "it's something you should find out in character." It's an IC job skill that you need some specific general game experience for in the first place if you want to do it to company standard (and thus get hired).
It sounds like you're playing at times of lower activity (the point of the post) so I imagine it might be tougher to organize, but I would try to seek a pro greeter to mentor you for now at least. Or even ask in pubsic. You never know what night owls might have been greeters once and are happy to share.
