I'm not on MFC, but in my experience with Skype, you often have to guide the conversation and keep it on track. The info you need boils down to: can you do the show he wants (activities, toys, outfit, etc. that work for you) and how long he wants the show to be. Once you've confirmed that what he wants is doable, you can remind him of the total payment amount, and then the ball's in his court. If a guy is serious about a show, usually he's fine with having the conversation efficiently and getting to the play time.
If I had to pick one single way to tell legit questions from timewaster questions, I'd say that yes/no questions are likely from a legit buyer (knows what he's after, just wants to know if you can do it), and open ended questions are usually a timewaster (wants to hear you talk at length about sexy stuff).
Questions that are typically legit: Do you have X toy? Do you have Y clothing item? Can you do A activity? Do you have B anatomical feature/talent? Oddly enough, I've found that a guy that writes a single, long-ass message describing what he wants and then asks if you can do it tends to be legit.
Questions that are typically from timewasters: What toys do you have? What anal toys do you have? What outfits do you have? What will you do in the show? What's your favorite roleplay? What's the biggest cock you've ever had? Any question that would result in sharing a dirty memory/story. I like silky panties; what kinds do you own? What kinds of heels do you have?
Can I have a preview? Can I pay less than what you charge?
Stuff that could go either way:
- A long string of yes/no questions that don't seem especially related, such as "Do you have a nurse outfit? Do you ever do shows outside? Do you do SPH? Do you cam from your house or a studio? Do you like nipple clamps? Could you make some cake batter?" I'd lean toward timewaster in these scenarios, but you can nip it in the bud early and ask him to just describe what he wants to do with you. Sometimes they are buyers that are overwhelmed by the possibilities or have a truly elaborate fantasy.
- A long string of yes/no questions that sounds like requesting free dirty talk, such as "Do you own a strap on? Is it big? Is it black? Would you make me suck it? Would you fuck me in the ass? Do you have a boyfriend? Is he black? Would you make me..." Probably a timewaster, but sometimes this guy is a buyer that needs a lot of hand holding. I don't recommend answering all his blow-by-blow questions. Again, you can nip it in the bud and get him to tell you what he wants, or you could give him an enticing answer that boils down to "I know where you're going with this. Stop asking questions and let me give you a wonderful and surprising time in the show."
- A lot of back and forth over a detail, such as "Do you have a long skirt?" "No, but would a full length dress work?" "Maybe, but does it show a lot of cleavage?" "Yes, it does." "But not too much, right? I don't want your bra to show. Ok?" This is a toss up. The guy is probably serious about a show, but what you can offer him may or may not work for his specific fantasy.
- Guys that plan out a show and then say they can't do it right now, but they'll come back later. Sometimes they actually do, but it's probably safer to go about your business assuming he won't. Some of these guys come back later... after 3 weeks.
As far as the 5 minute rule, that's pretty standard. After telling him that his show will be $X (or tokens, in your case), I give it about 5 minutes. If I've heard nothing back, I ask if he's having tech problems. If he doesn't respond pretty damn quick, I move along with my day.