I’m looking to house hack for my first purchase, but am not really looking to share living space with strangers.

You have to really understand the cultural norms in Belgium - is it normal & acceptable for people to regularly just rent out rooms in other people's homes, or a bunch of strangers to cohabitate in one home? 

Of course you can always just follow the advice of the "strangers" on this site.

Don’t listen to strangers on the internet.

Now, of course, this was my sister - I would not have given it away to just any stranger, but it does tell you that really did want the monkey off my back….So, I agree with most of the other answers: sell the thing “as is” either to the brother in law or on the open market.  

Plus they know you better than a stranger.

You are hiring the son of a stranger referred to you by a stranger.... 

I’m just curious if anyone has some useful tips for getting established as an agent, especially someone who isn’t necessarily efficient in small talk, ie approaching strangers, talking about my business.

You could deed the home to a passing stranger if you wanted to.

-> lockbox sounds interesting, but a little bit nervous about strangers coming in my property without me ever seeing them or knowing who they are.