What appid should I use with netsh.exe?
You can use any valid GUID. It is only used to allow you to identify the binding later.
I used the Application GUID for my WCF service that is located within the AsseblyInfo.vb (VB.NET) or AssemblyInfo.cs (C#) file of my hosting application (Windows Service) as show below:
<Assembly: Guid("8fbacae2-bd4e-8ef5-b202-1561845dd04f")>
I used this as the appid parameter for the netsh.exe tool like so:
appid={8fbacae2-bd4e-8ef5-b202-1561845dd04f}
It worked perfectly and my WCF service uses Https via that SSL cert.