You really don't need the Technic launcher for this.
First, go into your launcher, click "Launch options" and click the "Add new."
Once you click that, click version and select "1.4.2", then click the "Save."
After, click the little arrow next to "Play" and select your 1.4.2 version profile.
Run the game.
After running the game you need to install
Forge, click on "Universal" and click "Skip" at the top.
You then will have a .zip file, go into .Minecraft and go into versions. Open the .jar file with 7-zip, and drag the zip's contents in to the .jar file to replace them.
Now, run Minecraft 1.4.2 again. Go back into your .minecraft folder and create a folder called "mods"
Then, just download the 1.4.2 mods you want and paste them in the "mods" folder.\
Sorry for this post being a mess.