I use sarcasm quotes like so:
Let's ask the "expert".
But with a possessive noun, is the following the correct way, or isn't there one?
Let's ask for the "expert's" advice.
A- Let's ask for the "expert's" advice.
B- Let's ask for the expert's "advice".
Both imply something wrong. A implies either that the person isn't an expert, or that experts don't exist at least in this context. B could imply the same things PLUS that the advice isn't really advice - maybe it's an order.
For most circumstances, either would work so no rule.