I would not let a stranger use my loo,
unless they were actually in the house to e.g. deliver furniture, repair something, read meters
If I have already trusted them enough to let them in to work in my house, then I see no additional danger in them using the loo - I don't acompany them there.
I freely use the loo at work, including for a dump
Everywhere I've worked has a loo brush, so I use that if need be and rinse under the flush
My parents always had a loo brush;
I've always had one, with loo cleaner & air freshener nearby
I expect a civilised person to use these to leave the bathroom as clean & fresh as they found it
I must confess I always scrub the loo bowl, seat & sink with disinfectant after any visitor - including family or friends - and change the towels
The brush get rinsed after every use, as I flush
Important: it gets replaced regularly and immediately if it's grubby
I have NEVER stuck my hand down the loo
Now that would be a dirty habit, imo, even with (absorbent !) paper wrapped around the hand