how big is the texture anyways?
For a start, download vtfedit. install that.
Open up your blueprint in vtfedit.
I personally use,
normal format : BGR888
alpha format : BGR888
Texture type : Animated texture.
The max image resolution as far as im aware is about 4096x4096 which you might use if you were importing a highly detailed model texture. For your use, i think 2048x2048 is the very limit i would go for a mere blueprint. It would have to be a pretty bloody detailed blueprint if it was gonna be that big.
Make a folder in your textures folder called whatever you want. Save your blueprint in that.
Now click tools - create vmt file.
click on options and select what surface you want it to be (dont matter since nobody will walk on it or shoot it ever)
Click create and save it in the folder you made. (the same one as the blueprint you saved)
Your done. Open hammer and slap it on a brush.
Edit: wtfs a .skp file?