[quote=@Plank Sinatra]
Are our characters allowed to have any sort of pre-knowledge of the occult or demonology, or does it all have to come from association with the Slayer/spellcasting?[/quote]

Sure. You can have some knowledge--maybe not expert level, but yeah. There's tons of info out there...most of it's absolute garbage, but it's possible your character found a demon/vampire/supernatural website/message board on the dark web that's legit. It's possible they ran across a PDF of some tome that's not bullshit. So I'd say 85% of the information out there is bullshit, but 15% is actual information from primordial Earth and history. Your character could've stumbled across some of that 15%.

[quote=@Plank Sinatra]
Any prior experience with monster fighting allowed (since it's listed as one of the throwaway professions in the bio)?[/quote]

Yes. The group has been fighting supernatural stuff for around a year [b]already[/b]. They watched too much Stranger Things/Supernatural/etc, and when they noticed ACTUAL supernatural fuckery going on in Washington, they decided to act. So the Scooby Gang has about a year's worth of fighting lesser vampires, the odd lesser demon, maybe a monster of the week, etc. 

But serious stuff that goes "bump" in the night is on the way, and the Gang alone can't deal with it, they'll need the Slayer.