Required things
1. Alien Swarm ( its free! )
2. Portal 2 ( obviously )
3. Common sense ( cant do without! )

NOTE: Anything in brackets you MUST replace with your own file names!

First open up notepad and type in the following.

START "" "C:\Program Files (x86)\Steam\steamapps\common\alien swarm\bin\bspzip.exe"

That will simply open up bspzip, this bspzip supports portal 2's bsp version (21). The next thing you need to do is put in the parameters for bspzip to put your textures and sounds and such into your map simply type this in right next to what you typed before do not press enter at all during any of this.

"-addfile" "C:\Program Files (x86)\Steam\steamapps\common\portal 2\portal2\maps\[yourmapname]" "[your sound, texture, etc]" "C:\Program Files (x86)\Steam\steamapps\common\portal 2\portal2\[your sound, texture, etc]" "C:\Program Files (x86)\Steam\steamapps\common\portal 2\portal2\maps\[yourmapname]"

Heres an example of everything put together

START "" "C:\Program Files (x86)\Steam\steamapps\common\alien swarm\bin\bspzip.exe" "-addfile" "C:\Program Files (x86)\Steam\steamapps\common\portal 2\portal2\maps\sp_gravity_trials1.bsp" "sound\br\epic.wav" "C:\Program Files (x86)\Steam\steamapps\common\portal 2\portal2\sound\br\epic.wav" "C:\Program Files (x86)\Steam\steamapps\common\portal 2\portal2\maps\sp_gravity_trials1.bsp"

Now that you have told bspzip what to do simply save the file anywhere your computer and name it "[yourname].bat", run it, open portal 2, open map, and enjoy your zipped in customs.

UPDATE
I almost forgot this, THE ABOVE WILL ONLY WORK FOR SINGLE FILES TO ADD MULTIPLE FILES VIEW BELOW

Adding multiple files is not as easy as adding single files and is in fact alot more confusing.

First thing you need to do is type in the following into a notepad document

START "" "C:\Program Files (x86)\Steam\steamapps\common\alien swarm\bin\bspzip.exe"

Yes it is the same as the single one but the parameters are where it gets harder because of the fact that BSPzip requires there to be a full list of all the files you want to add into your BSP. To make this work you will need to create one of these lists by doing the following

open up a new notepad window and type in the following again REPLACE ALL BRACKETS WITH YOUR FILES!

"[your first texture, model, sound, etc here]"
"C:\Program Files (x86)\Steam\steamapps\common\portal 2\portal2\[your first texture, model, sound ,etc here]"
"[your second texture, model, sound, etc here]"
"C:\Program Files (x86)\Steam\steamapps\common\portal 2\portal2\[your second texture, model, sound ,etc here"

That is the basic structure of your list you can name it anything you want as long as its a txt file, heres an example of what it should look like.

"sound\br\epic.wav"
"C:\Program Files (x86)\Steam\steamapps\common\portal 2\portal2\sound\br\epic.wav"
"sound\br\epic.wav"
"C:\Program Files (x86)\Steam\steamapps\common\portal 2\portal2\sound\br\epic.wav

In a short explanation the shorter file paths are where the file will go after zipped into your BSP and the longer ones are where the files are located on your hard drive. Now that you have created your list and saved it the process gets a whole lot easier, just type the following text into your first notepad window

"-addorupdatelist" "C:\Program Files (x86)\Steam\steamapps\common\portal 2\portal2\maps\[yourmapname]" "[file list location]" "C:\Program Files (x86)\Steam\steamapps\common\portal 2\portal2\maps\[yourmapname]"

You can also replace -addorupdatelist with -addlist but the -addorupdatelist parameter will allow you to add new files to the same text file and then update your zipped files easily.

Hope this helps alot of you mappers out there!

msleeper wrote:
There's already a GUI for this, it's called Pakrat.

though pakrat doesn't work with portal 2 i have already tried it