I wanna post some stuff from some Twitter artists who simply aren't here, but tagging might be a little hellish. Could I do a few core tags and just leave it up to other people or do I gotta go over each one?

You can at least do the bare minimum. It's not "hellish", tagging usually only takes 2-3 minutes per post.

This is the stuff that you should do:
– artist tag, always. Make one if one does not exist.
– character count: solo / duo / trio / group
– character gender: male / female / gynomorph / andromorph / herm / maleherm
– body types: anthro / feral / taur / humanoid
– species: canine, feline, bovine, cervine, etc
– genitalia, if visible: penis / pussy / anus / breasts
– activity: if the characters are standing / running / cuddling / having sex, that sort of thing
– blacklistable content, such as vore, scat, gore, etc

These are the tags that let other people find the posts you have uploaded.
If you want to be more thorough, you can add more detailed tags, such as:
– fur / skin / scales / feathers color, including hair
– penetration (ex. male_penetrating_female, anal_penetration, etc)
– background (ex. simple_background, detailed_background, landscape, etc)
– location (ex. inside, outside, bedroom. cave, field, kitchen, forest)

These are excerpts from a longer tagging checklist, if you are curious.
You don't have to upload literally everything at once. You can just start posting 5 images a day. It's better for votes and favorites too, as the front page does not get overwhelmed with samey stuff.

The upload page will walk you through the basics: artist, characters, etc. Tag whatever's going on in the picture, and you've done enough that other taggers can help.

tagging is really really simple. You tag what you see, that's all.
It can even be down to the mudane such as eye and hair color, their outfit, the background...it's not hellish.

That does sound very sweet of you but it might be important to message them on twitter as well that - in case they want to see comments or likes etc. And maybe they will get into the habit of doing it.
For your queries there might some basic tags you can use as well which has already been mentioned further up in this thread.