Please know that portal 2 has had an update... You used to be able to just open the publishing tool and click browse files. There is now extra steps involved, which is REALLY annoying. You will need to download the file from [Insert Link here] in order to continue.

Step 1: Download the file onto your computer and put it a folder somwhere easy to access.

Step 2: If you don't already have Winrar or 7zip... This is the time to get it as there is no other way to do this.

Step 3: Move the following 3 files from your portal 2/bin to a place where you will not lose them:
inputsystem.dll
localize.dll
steam_api.dll

Step 4: Extract the files from the folder of fix into your bin folder of portal 2

Step 5:Run p2publish and publish all your maps that you would like to publish.

Step 6: Once done publishing move the 3 files from your safekeeping folder back into portal 2/bin. When it asks you to replace the files click yes.

Step 7: Continue playing portal 2! Hope you enjoyed.

NOTE: Requires being able to download maps without the workshop, easy video:
https://www.youtube.com/watch?v=Lm6Dx32YIrw

The goal of the map is to prevent cubes from getting to the end! Good luck!

Map 1:
http://forums.thinkingwithportals.com/downloads.php?view=detail&df_id=1378

Map 2:
http://forums.thinkingwithportals.com/downloads.php?view=detail&df_id=1438

Now the trick to doing this is both people must have the map... Then load up normal coop mode... Then in console tpye "Changelevel [levelname]"

For an example, I would type "changelevel mp_coop_tower_defense"
For the second map I would type "changelevel mp_coop_tower_defense_2"

Note all credit goes to;LuckyRj:
Have two info_targets called "supress_orange_portalgun_spawn" and "supress_blue_portalgun_spawn".

In the portal 2/bin folder find P2map_publish.exe and open it
Select 'Add'
Under 'Preview Image' select 'Browse' to choose your main image
Under 'File' select 'Browse' for your P2 map
Check 'Steam Workshop Agreement'
Click 'Publish' to add your file to the workshopworkshop

These Hammer Tutorials are about setting up a key code combination, in which a set of buttons must be pressed in a certain order before a door will open.

Tutorial 1 by Lee Davis:

You will need:
1 prop_testchamber_door
4 prop_button
4 logic_compare
1 logic_relay

STEPS:

Names:
1. name each prop_compare appropriately (ex. Compare_first, Compare_second, etc)
2. Name the logic_relay (ex. Relay_reset_code)
3. Name prop_testchamber_door (ex. door01, works for me)

Values:
Set the first compare_#### Property "Compare Value" to 1.0

Outputes:
1. Set all prop_buttons to ONLY activate ONE logic_compare EACH. (ex button01 controls Compare_first, button03 controls Compare_third, etc)
Set all buttons to these Outputes:
OnPressed "ENTITY" Compare_#### "INPUT" SetValue "PARAMETER" 1.0
OnPressed "ENTITY" Compare_#### "INPUT" Compare "Delay" 0.1

2. Set all logic_compares to these outputes, EXCEPT THE LAST COMPARE:
OnEqualTo "ENTITY" Compare_next_compare "INPUT" SetcCompareValue "PARAMETER" 1.0
Last Compare_#### must be set to open the door instead
(ex OnEqualTo "ENTITY" door01 "INPUT" open)
3. Skip the first compare, and add this outputs to the rest of the logic_compare
OnGreaterThan "ENTITY" relay_reset_code "INPUT" trigger

3. Set the logic_relay to these outputs:
OnTrigger "ENTITY" compare_#### "INPUT" SetValue "PARAMETER" 0.0
REPEAT THIS SO ALL COMPARES ARE RESET TO 0.0

Except for the first compare_###, add this For the rest of them.
OnTrigger "ENTITY" compare_#### "INPUT" SetCompareValue "PARAMETER" 0.0
REPEAT THIS SO ALL COMPARES ARE RESET TO 0.0 (EXCEPT THE FIRST COMPARE_####)

That is it....test in game and see it working.
Thanks.