DItto on Bob Moffatt. No BS and good technique.
All the wires run a little different. You will most likely end up with a roll of Lincoln NR211-MP (or Hobart 21B). It will like to run under 18V. You can figure wire speed by holding the trigger for 10 sec, measuring the wire, and multiplying by 6. After you get the hang of it, you'll be able to dial speed and voltage by feel/sound. The chart below is right off the Lincoln site.
I run a lot of fluxcore, but it's mostly larger wire, out of a suitcase feeder. Fluxcore is a lot more capable than most people give it credit for.
This is 1" plate welded with fluxcore. .068" NR203-MP at about 225A. Not even close to max capacity for that wire.
Fluxcore will have no problem wetting-in with correct settings
The biggest thing with fluxcore is to not let the arc leave the puddle. Move the puddle with you, or you'll get slag inclusions. Self shielded wire runs the opposite polarity of MIG hard wire with gas. You want it set up with the negative lead hooked to the feeder/gun for DC-. NR211 doesn't like to weld over any old slag, so clean between passes. You can trim the gas nozzle back to better see the contact tip, or run without it. It's nice to have it on to keep the dingle berries from funking up the gun diffuser/tip. Fluxocre also like more wire stickout from the tip to the work to give the flux inside time to preheat. Sometimes the puddle will become kind of hard to see with the slag floating. That usually is from letting the slag get ahead of the arc and muck up the puddle. Best is to stop, chip slag on the the puddle, then restart. Almost always use a drag technique, pulling the puddle along. Pushing won't get much penetration and lead to trapped slag under the bead.
Greyson