First of all copying code from demos is defiantly not the way to learn.
Best thing to do if really want to copy code is to type it line by line (using intelligence really makes this fast) as this way you will get in your head what each line does way better than just reading it.
Also these brushes are just debug stuff for Farseer essentially, Farseer of course assumes that you already know how to program at least basically...
And you must know how to render sprites and stuff (You have done the samples from the XNA site right?)
once you have a basic understanding of programming with c# and have made a lot of small little apps, only then are you ready for a physics engine.
A physics engine is not a small thing; Farseer makes it so ridiculously easy it’s not funny.
Farseer is not a rendering engine.
You can get a physics engine with a 2 box’s in it in about 5 lines of code.
//Not real code but almost
physicssimulator thephysicssimulator =
new physicssimulator(vector2 gravity);
Body bod1 = bodyfactory.get.createbox(thephysicssimulator, vector2 size, mass);
Geom geo1 = geomfactory.get.createbox(thephysicssimulator, od1, vector2 size);
Body bod2 = bodyfactory.get.createbox(thephysicssimulator, vector2 size, mass);
Geom geo2 = geomfactory.get.createbox(thephysicssimulator, bod2, vector2 size);
//Now just render it using a sprite (XNA FORUM IF YOU DONT KNOW HOW)
spriteBatch.render(yourSprite1, bod1.position, bod1.rotation);
spriteBatch.render(yourSprite2, bod2.position, bod2.rotation);
And that’s it all done, you now have 2 box’s rendering (using sprites)
and in the physics simulator (they will just fall thou)
Also all of this is in the simple samples (they are called that for a reason)
They really do have the bare minimum and as long as you can ignore the rendering code (which is needed so you can see the demos)
The demos are written in a way that is easy to understand while being easy for the dev's to keep updated and fast to write as this gives them more time to work on the new versions of Farseer (which is what we all want)
The first 3 demos are all focused on simplicity first and foremost if you cannot already make a small game without Farseer then you defiantly cannot make on with it.
I think you should try some of the XNA samples first until you understand how the whole rendering and movement process works first.