Some of you will have heard of the Slammin' Source Tools from a facepunch thread. You can read up on all the improvements it has over the stock hammer editor or compiling tools under this link.
A drawback of the tools was that they wouldn't work for tf2 without installing the Source SDK base 2013 Multiplayer tools - this patch remedies that, and you can now use the tools as-is with tf2 - no external source downloads required.
This method override no files in the tf2 directories, and you can choose to use only the hammer or the compile tools based on preferences. I would personally recommend only using the slammin' compilers if you really need to, however the vrad_patch.exe is highly recommended as it is identical to stock VRAD aside from being multithreaded - this gives compiles that are far shorter than with stock hammer, and the faster your CPU the greater the benefits.
Slammin' hammer: https://tf2maps.net/downloads/slammin-source-tools-v2-hammer.9286/
VRAD patch: https://tf2maps.net/downloads/vrad-patch.9288/
Improvements to the tools over the normal Slammin' Source Tools:
*No external SDK download needed - you just drag and drop the files into your Team Fortress 2 install, set up a shortcut, and you can start using them straight away
*vrad_patch included - a simple edit of the stock vrad.exe, the only change being multithreading. This means compiles are far faster than normal vrad's for both HDR and LDR, without any disadvantages
*Move the contents of the /bin/ folder to /Team Fortress 2/bin/
**Your path should be /Team Fortress 2/bin/<.exe and .dll files> after this
*In hammer, go to Tools -> Options -> Build Configurations, and set up the path to whichever modified compilers you wish to use.
*Compile your map
Full credits to Ficool2 for this patch, and slartibarty for the original Slammin' Source Tools.
NOTE: be wary when using a mix-and-match of slammin' compilers with other compile tools (like stock vrad with slammin' vbsp and vvis) - it may cause issues with the compile despite no clear errors
Simple speed comparison, note this is not representive of the benefits on all maps and CPUs: