Create a file that contains instructions to use the RealTimeStylus functionality. To enable the RealTimeStylus functionality:
Create a text file in a text editor such as Notepad and type in the following lines:
Save the file as a plain text file named PSUserConfig.txt, and save the file into the Photoshop settings folder: C:\Users\[User Name]\AppData\Roaming\Adobe\Adobe Photoshop CC\Adobe Photoshop CC Settings\.
To turn off the RealTimeStylus functionality, delete the PSUSerConfig.txt file. Or, move it to a different folder if it doesn't contain any other commands, or change the lines so they read:
Credit to the Sony Community forum and user Keiran for the above.
The above only works with Photoshop CC and didn't work on CS6. For CS6, download and install the N-Trig drivers for the Surface Pro 3 from http://ntrig.com/Content.aspx?Page=Downloads_Drivers
Make sure Photoshop is not running when you do any of the above.