If your company is planning on hiring 4-6 technical people a year, your next hire should be a recruiter. It is probably best if they do not have experience being a recruiter or a salescritter. Hire someone with a liberal arts degree or technical communications experience.
If your company is hiring more than that, why don’t you already have an in-house recruiter?
External recruiters are lying spammers. It’s the nature of the economics: they don’t get paid until they land a candidate, but they can’t afford to learn enough about your company or the role to get good candidates, so they need to work in bulk. An external recruiting company wants 20-30% of first-year salary as a fee. If you’re hiring 5 people a year, you can afford to pay an internal recruiter the average of their salaries, which should be quite nice indeed - external recruiters are paid on commission, which induces feast-or-famine responses and consequent unethical practices.
An internal recruiter can talk to your hiring managers, ask questions, and build trust. An internal recruiter is inherently more trustworthy to a prospective candidate, too: they can reference the company’s name from day one, and can offer actual details immediately.