Got it, connected it to vac, used it with toothed-style box sinker.
It worked surprisingly well at capturing dust.

After ordering it, I got an email from the seller that said...

"Did you know you can also use your Dustbuddy with box sinking tools
such as Armeg? Simply fix the Dustbuddy to the wall using a 3" screw,
once finished unscrew the Dustbuddy and fill the screw hole."

....although I guess this was an afterthought when it had gone into
production as there are no fixing holes or tabs included in the
design, although it would obviously be easy enough to drill a hole in
it somewhere.

In this instance, I held it in place as I didn't want to damage
surrounding decoration or take any more risk with crumbly 1930s
plaster. Not particularly easy to use on your own, one hand holding
this and the other the SDS. Would be much easier with a partner.