Almost the same as a black mirror in its effect, but better in practice, much easier. On PC would work more effectively.
If you didn’t see anything then try going deeper in TGS that’s the only thing needed. You’re not “waiting” for something to appear… but you need to know it’s already there, you just can’t see it yet. The image and trance will allow you to see it.
I think it’s a different technique than dowsing, so can’t compare between them. Each one got strength and weaknesses. For example, dowsing is more practical because it can be done anywhere anytime. But this technique is better if you’re looking for more detailed answers that dowsing can’t provide.
Yes I believe you can, as long as it doesn’t empower your lust for result.