Not all pen nibs are created equal. Some are much more flexible, making thin-to-wide lines possible in the same stroke by varying pressure. That takes practice to master, but makes for good artwork.
If you're snagging on everything, make sure that your holding the pen right-side up (that's the newbie mistake I made for awhile. You want the sides to curve down towards the writing surface).
It is super easy to bend the tip and ruin a pen. Just dropping it once on the floor can render the thing useless. Also, if you've been practicing on cheap paper, watch for tiny paper fibers caught in the tip.
Caligraphy ink comes in quite a few colors. I've found the plain old black ink flows much easier. I've got to believe that acrylic paint will dry too quickly and clog your pen nib. I picked up some "Dr. Ph. Martin's Bombay" in white at Hobby Lobby that worked tolerably well. Red in the same brand flows better, and drys flatter. I'd suggest practicing with the cheap black ink Wal-mart sells and a Speedball #512 nib.
Ok, now if I only knew more about actually building bows....