Since the topic of converting ASMX web service to WCF is already well covered on the internet: (e.g.)
- http://msdn.microsoft.com/en-us/library/aa738697(v=vs.110).aspx
- http://www.codeproject.com/Articles/312490/Migrating-ASMX-Services-To-WCF-services
- http://blogs.msdn.com/b/kaevans/archive/2006/10/05/phased-migration-from-asmx-to-wcf.aspx
I suspect that you are looking for a way to “shortcut” the process. To that end, I think the implementation of WCF Web Services is sufficiently straightforward that any workaround compromises will not be worthwhile. Therefore, my advice is to prioritize your web services and start converting.
Good luck.