cash is king as others have already stated. If the provider doesn't accept cash then I'm with the wrong person. If it ever gets to the point where cash is no longer accepted as payment then I'll find another hobby.
Knowing how traceable electronics are these days makes me wonder how wise it is to move money this way. Somewhere in cyberspace there has to be a record of these electronic transactions and it's gonna be used by the feds against the providers in this industry either in building prostitution charges, tax evasion charges, or both. Especially if the servers are based in the USA or somewhere where the DOJ can put pressure on to gain access to records if not just invade and seize outright.