First make sure you have all the programs listed below installed (or similar programs, you can use any slicer)

Here are all the programs you will need with download links:

GCFScape:
https://nemstools.github.io
GCFScape is used to extract the model files

Crowbar:
https://steamproxy.net/groups/CrowbarTool
Crowbar is used to unpack the model files

Blender:
https://www.blender.org
To convert from source model file to STL/3MF

Blender Source Tools Addon:
https://steamproxy.net/groups/BlenderSourceTools

Microsoft 3D builder (comes with windows 10):
To fix the 3D mesh after converting in blender
https://www.microsoft.com/en-us/p/3d-builder/9wzdncrfj3t6#activetab=pivot:overviewtab

Cura(the slicer I use):
https://ultimaker.com/software/ultimaker-cura
To slice for printing.

First, open GCFScape and click "file>Open>" Then navigate to your \steamapps\common\Team Fortress 2\tf folder.

Now, Look for a file called "tf2_misc_dir.vpk" and select it, once you've selected it press open.

Now that you have the directory file open, navigate to the "models" folder and look for the specific model you want to extract.

Weapon models are in the "Weapons" folder and hats/items are in the "player" folder, other models will be in other folders, just look around a bit.

Once you find the model you want to print, select ALL the models files and right click and press extract and save the files somewhere(i use my downloads folder as a temp).
Now that you have the files extracted on your pc, you need to unpack them using crowbar. Open crowbar and go to the "Decompile" tab. For the input folder, select the .mdl file you just extracted and set an output folder to something on your desktop or downloads.

Now press the big "Decompile" button in the bottom left and then check your outpuit folder to be sure it worked. (you should now have a ".SMD" model file)

Now, open blender and make sure you have blender source tools installed so you can import the .SMD file you just decompiled. Once you have blender open, clear the worspace and go to "file>import>Source Engine" and select the .SMD file you decompiled in the last step.

You should now see the full model in blender, from here you need to go to File>Export>Export As .OBJ (or STL if you wanna skip the next step, which fixes some broken models)

Now, Open 3D builder and import the .OBJ, it should ask if you want to automatically repair it in the bottom right, click yes and then go to file>export> and export as an STL or 3MF

Now Open your slicer and import the STL/3MF and get to printing! Good luck and lmk if you have any questions/just wanna show off what you made down below. Here are a few test files if you dont want to do the work yourself https://www.prusaprinters.org/social/179217-newport1/prints

Thanks for reading and leave a thumbs up if this guide helped! And if you really wanna help me out, download the test model from the prusa site (I get free filament if i get enough) this is my first guide so sorry about formatting.

I may update it later with more photos but for now, heres the video I made on how to do it if you want to see someone do it in detail. (and the lugermorph I printed)
https://www.youtube.com/watch?v=nq65Lhf0REk

update: Here's an example of an incendiary grenade pulled from csgo just to show it can be done.