My strategy for filtering out timewasters is:
Ask what time they're coming and give my prices. If they keep asking questions and don't give a time, ignore and move on
If they give a time, I ask them to text a confirmation reply and end the call. No confirmation reply, I don't get ready. Timewasting callers don't bother to follow through with this 90% of the time. If they confirm but don't show up, block.
I don't take bookings more than an hour in advance. 90% of guys saying they will come the next day or "later" are timewasters.
Ignore anyone asking for pictures or whatsapp immediately. Plenty photos of me on my profile for them to make a decision and the only reason why a client wants your whatsapp is to hassle you for free pictures and chat.
In general the golden rule is the more questions they ask and the more vague they are about when they are coming the less likely they are to turn up.