I have been providing technical support and consulting for over twenty years and I can assure you, no one knows the answer to every question, and even trying to keep up with changes in technology is more than a challenge, it is impossible.
Knowing where to look, or not to look, for answers is sometimes the key to providing excellent tech support and consulting.
My consulting fee is $100.00 per hour, and one hour minimum.
When a person calls, saying they want "a little information" and proceeds to pick my brain, the fee is the same as regular consulting.
If a person has me doing some work for them, and I am answering questions, my rate is the rate for the work I am doing.