As a Founder and former turn-around executive validating a business idea is a key requirement before spending capital on implementation.
This is also a task that has to be handled by the originator of the idea so it cannot and should not be contracted out.
My technic when doing an idea validation is to start out with my first degree network (Friends, Peers and Relatives) and then my social network.
My approach is to create an opportunity for a one on one conversation that is not under time pressure and allows for open ended answers.
The key is that after I outline the idea I mostly listen and take notes.
Also whie preferrable, the conversation partner does not need to be in the same industry that the idea is covering. The best insights often come from the least expected source.
Best Wishes,
Herb