He’s an introvert but that shouldn’t really matter cuz a lot of tech folks are introverts.
In that case its time to show and prove if he wants an in. Not his field but lets say he worked in cyber security he could sniff the network, escalate then
send the CEO an email from himself mentioning how he should employ him then tell him to check his schedule for the appointment he's already booked in using his secretaries credentials.
Thats the script, he'll just have to adapt it to his environment, if he has the skills. Thing is with the field is that its oversubscribed in the areas everyone picks and thus there is a handful of star players that are up on whats really needed. Lots of solid C class coders but only a few A+++ all day who make the pay grade. People training now to catch up are too late because those one step ahead are rinsing the current prospect whilst quietly learning whats next because they work at the cutting edge so its always the same horses leading the pack.
Introvert or not its the network that will get him the placement as he'll know about the script because programmers roll with crews and always pull their team in as that increases their access to information which means they'll be one step ahead again. The firms are also remarkably lazy in upping someone pay unless you step to em because they bank on the programmers being meek and taking what they're given vs any possible anxiety they may feel when saying "Give me more or I leave". Actually I've just had an idea:
Tell him to find a specialist recruiter (the kind that charges a placement fee) and ask him to appraise his CV and chances. That will show him the lay of the land and may just land him an interview because outside of personal recs the recruiter has next.