Usability testing is typically the most mature and straightforward form of discovery testing, and it has existed for many years. The tools are better and teams do much more of this now than they used to, and this is not rocket science. The main difference today is that we do usability testing in discovery—using prototypes, before we build the product—and not at the end, where it's really too late to correct the issues without significant waste or worse.
If your company is large enough to have its own user research group, by all means secure as much of their time for your team as you absolutely can. Even if you can't get much of their time, these people are often terrific resources, and if you can make a friend in this group, it can be a huge help to you.
If your organization has funds earmarked for outside services, you may be able to use one of many user research firms to conduct the testing for you. But at the price that most firms charge, chances are that you won't be able to afford nearly as much of this type of testing as your product will need. If you're like most companies, you have few resources available, and even less money. But you can't let that stop you.
So, I'll show you how to do this testing yourself.
No, you won't be as proficient as a trained user researcher—at least at first—and it'll take you a few sessions to get the hang of it, but, in most cases, you'll find that you can still identify the serious issues and friction points ...