OWIN Security - How to Implement OAuth2 Refresh Tokens

I am using the Web Api 2 template that comes with Visual Studio 2013 has some OWIN middleware to do User Authentication and the likes of.

In the OAuthAuthorizationServerOptions I noticed that the OAuth2 Server is setup to hand out tokens that expire in 14 days

 OAuthOptions = new OAuthAuthorizationServerOptions
 {
      TokenEndpointPath = new PathString("/api/token"),
      Provider = new ApplicationOAuthProvider(PublicClientId,UserManagerFactory) ,
      AuthorizeEndpointPath = new PathString("/api/Account/ExternalLogin"),
      AccessTokenExpireTimeSpan = TimeSpan.FromDays(14),
      AllowInsecureHttp = true
 };

This is not suitable for my latest project. I would like to hand out short lived bearer_tokens that can be refreshed using a refresh_token

I have done lots of googling and can't find anything helpful.

So this is how far I have managed to get. I have now reached the point of "WTF do I now".

I have written a RefreshTokenProvider that implements IAuthenticationTokenProvider as per the RefreshTokenProvider property on OAuthAuthorizationServerOptions class:

    public class SimpleRefreshTokenProvider : IAuthenticationTokenProvider
    {
       private static ConcurrentDictionary<string, AuthenticationTicket> _refreshTokens = new ConcurrentDictionary<string, AuthenticationTicket>();

        public async Task CreateAsync(AuthenticationTokenCreateContext context)
        {
            var guid = Guid.NewGuid().ToString();


            _refreshTokens.TryAdd(guid, context.Ticket);

            // hash??
            context.SetToken(guid);
        }

        public async Task ReceiveAsync(AuthenticationTokenReceiveContext context)
        {
            AuthenticationTicket ticket;

            if (_refreshTokens.TryRemove(context.Token, out ticket))
            {
                context.SetTicket(ticket);
            }
        }

        public void Create(AuthenticationTokenCreateContext context)
        {
            throw new NotImplementedException();
        }

        public void Receive(AuthenticationTokenReceiveContext context)
        {
            throw new NotImplementedException();
        }
    }

    // Now in my Startup.Auth.cs
    OAuthOptions = new OAuthAuthorizationServerOptions
    {
        TokenEndpointPath = new PathString("/api/token"),
        Provider = new ApplicationOAuthProvider(PublicClientId,UserManagerFactory) ,
        AuthorizeEndpointPath = new PathString("/api/Account/ExternalLogin"),
        AccessTokenExpireTimeSpan = TimeSpan.FromMinutes(2),
        AllowInsecureHttp = true,
        RefreshTokenProvider = new RefreshTokenProvider() // This is my test
    };

So now when someone requests a bearer_token I am now sending a refresh_token, which is great.

So now how do I uses this refresh_token to get a new bearer_token, presumably I need to send a request to my token endpoint with some specific HTTP Headers set?

Just thinking out loud as I type... Should I handle refresh_token expiration in my SimpleRefreshTokenProvider? How would a client obtain a new refresh_token?

I could really do with some reading material / documentation because I don't want to get this wrong and would like to follow some sort of standard.