Luckily we don't have to face lots of spam due to our more complex registration process (SSO). This way only very few spam users are created (maybe one every few months or so).
We also are lucky to have very active and very "vigilant" super users. They can either use the "flag" function in the frontend, or use their access to the control panel and therefore mark comments as "spam".
When it happens after hours, our team will review the flagged content when they start working again. Also, we have a whatsapp group that our super users can use to notice the others of ongoing problems (not only spam, also outages and other issues).
I think your way of manually dealing with it already is very good. You even have a direct (whatsapp) communication going on for urgent matters.
The only thing that might benefit you is a better automated anti-spam function so the manual effort will be further limited.
I actually do not know what happens when you mark a post as spam. Can anyone tell me?
@Danjl maybe in addition to what others said, I would also make sure to be registered for the Email alerts ([Forum settings] - [Email alert]): all Mods should have added their email listed there. You will always get a mail with all relevant info right-away, this is the best practice. Whatsapp is fine, especially out of office hours, but these mails are more reliable.
Once somebody starts to spam, I usually keep an eye on the registrations for the next hour, just to be on the safe side. They like to try it again, but the quicker you ban them, the less likely they will come back. So reacting quickly actually is the best way to keep them away in my book.
We are steadily improving our platform to detect and prevent spam, e.g. with email-checks (no registration when it's a known spam account) as a recent addition. However we are also looking into other options, e.g. front-end Moderation rights like described in
this idea.
Unfortunately the spammers can be quite creative trying to get through our checks, and it can be a challenge to fight them without hindering regular users from posting...