Usually we have several scenarios:
1) It's ideal one - the customer knows exactly what he wants, has functional requirements and technical specification. In that case all you need is to ask for those two documents and send all the information to us. We'll make the estimation.
2) The most popular scenario is when the customer understands what he wants but doesn't have the functional requirements and technical specification. In this case you can share with the customer this file - it's a template
for functional requirements and technical specification. I suppose the customer has an internal technical specialist on its side who can insert all necessary information. In case of any questions, we have technical specialists that will answer all the questions about that template. We can arrange Skype call for both sides and act like translators for them or mail the list of questions to each other. There are a lot of ways to communicate. This scenario is usually used by the customers that have strong intension to cooperate.
3) Also we have the customers that are lazy enough to insert the info about functional requirements to that file but they have money and would like we to do that for them. In this case we have this service in our price list - tehnical analitics. In this case we offer english speaking technical specialist that can contact the customer directly and ask for all the information, then insert it in a template. But the customer should understand that this is also need time from several hours to several months (in case of really huge projects). In some cases we can hire translator to help to communicate with a customer's technical specialist.
It's our experience of working in other countries, but you can offer any other idea you think will work for your customers. We are open to discuss any other cases.