How do I set up FTP access to Azure App Service?

In the Azure Portal:

1. click on your App Service that you'd like to access from FTP.
2. On the Overview tab for your App Service, look at the top navigation bar and click on the "Get Publish Profile" link. This will download your publish profile.
3. Open the downloaded publish profile (it's a text file). Your FTP credentials are there.

I do not believe you can use multiple methods to publish to an App Service. I think it's limited to one. However, you are not locked into that one upon creation as you can change it from Deployment Center. Thus, you can't both publish your app from Visual Studio and FTP upload your app.

However, if you want to FTP for other reasons, you can piggyback on the ability to FTP for diagnostics logging. If you click, Diagnostics logs under Monitoring, you will find your FTP URL for your App Service and the user name needed for FTP. This leaves one issue as you need to setup a password for FTP. If you go to Deployment Center > Deployment Credentials > User Credentials, you should be able to update your password for the App Service FTP server. Thus, you'd be able to access your App Service from FTP.

For more information, you can check out this document from Azure.