I went through this same experience over the past year and a half. At some point I intend to write a more detailed blog post about my process, but the short version is that I did a boatload of research ahead of time, and leveraged the heck out of my network. In places where I found my network to be lacking, I invested additional time/effort to build connections. I had more success through networking and personal connections than I ever did via resumes or direct submissions. I didn't work with any recruiters, so I don't feel qualified to speak to their effectiveness.

I actually have some experience interviewing.io. I initially starting using it as a way brush up on my technical interviewing skills (it had been years since I was last an interviewee vs. interviewer) and it ended up being through interviewing.io that I was introduced to Mattermark where I was eventually hired. It was a great tool to have in my job-hunting tool belt as I was able to 1) brush up on my tech interviewing 2) meet/network with interviewers (when an interview went well) and 3) do a few 1st round interviews with a couple of prospective companies.

I wouldn't use interviewing.io as my only means to land an interview with a company. Especially since everything is anonymous, and thus only in specific circumstances do you know the company that your interviewer is associated with. But it was a great way to do low/no risk interviews that at least had the potential to count as a first round interview.