Well the answer to this has 2 parts. First of all, just drawing it huge and then shrinkin doesn't reall give you smooth lines automatically. You have to learn some smoothness on your own. As far how Jeph does things, he starts all the QC panels as 4800x2800-pixel (the new, wider ones are different) images in photoshop and then shrinkks them down to what you see on the site which is something like 15 percent of the original size.
good luck!