The process that Facebook, and many other social media sites, employ are there specifically so that third-party applications, or websites, can not post content to walls without a user's consent. There is really no way to get around this UNLESS you have already had the user authenticate your application and can "regenerate" your token. The user needs to log in to Facebook to allow your app access anyway, so unless you're asking for their credentials, there is no real way to automate this process for your user(s).
The only alternative I can think of is to use an iframe which is where all the redirection happens. So your URL would be something like mydomain.tld/facebookauth but the content would be purely just an iframe which displays the facebook page. To your user, it looks like facebook is loading but the URL doesn't match. This goes against every security agencies recommendations which is to check that the URL matches the content. I would not suggest the iframe approach as it can cause too many issues.
Why do you need to mask the fact that you're going to be putting content on someone's facebook page/wall?
