Here's what I do...
I cut out and sand my fins to the appropriate airfoil. I take regular printer paper and cut out large sections about double the size of the fin with at least an inch or two all the way around extra. I put a big drop of white glue on the lower half of the paper, spread it out thinly with a finger or old credit card, and press the fin down fimly onto the paper, and 'squirm' it around in a little circle a bit to smear the glue well between the paper and fin and squeeze the excess out around the edges. I align the leading edge with the middle of the paper, flip it over, and using the round end of a Sharpie marker, I burnish the paper firmly onto the fin, squeezing 90% or more of the glue out from between the paper and fin.
Flip it back over, smear another big drop of glue on the remaining upper half of the paper ('drop is a relative term-- for large fins you may have to smear a few lines of glue around into a uniform layer, and I'd DEFINITELY use a credit card or other squeegie to spread the glue evenly and thinly and uniformly)
Fold the fin over onto the top half of the paper AT THE LEADING EDGE. Keep the paper firmly but gently pulled taut as you fold the fin over onto it at the leading edge. Again use your round Sharpie end to burnish the paper down smoothly, firmly, and evenly, and squeeze the excess glue out around the tip, trailing, and root edges. The paper should be firmly adhered and wrapped over the leading edge, so burnish from the leading edge rearward and outward. Once the fins are done, sandwich between two sheets of wax paper and put a book or something flat and heavy on them overnight to dry.
Once dry, take a hobby knife with a new SHARP blade and trim off the excess paper back to about 1/4 inch or less from the edge, and then CAREFULLY 'shave' the remaining paper off the tip, trailing, and root edges. If you use a gentle 'shaving' motion, the paper will gently, crisply, and cleanly curl right off the edge of the balsa and leave a perfectly smooth and clean edge on the fin. Sometimes you'll get a few stray 'paper hairs' which are easily shaved off by drawing the fin TOWARDS yourself across a sheet of 240 grit sandpaper (or finer) with just a SLIGHT tilt towards you as you pull it gently across the paper. You can also take off any excess glue that didn't get shaved off at the same time by drawing the fin across the sandpaper with it standing at 90 degrees to the paper.
I have been using this method and I don't see the need for using the label paper because it does SUCH a terrific job! Folding the paper over the leading edge means that not only is there NO seams to come loose, but the airflow is working against solid uncut paper at the leading edge-- far better (to me anyway) than having the airflow ripping at the edge of paper glued to the balsa at this area, forming an easily seperated seam that would be difficult to glue back down (I've seen WAY too many peeling, curled labels in my time and they're nearly impossible to get to stay down again).
White glue works well for this, as white glue is best for gluing paper to anything else. You CAN CA the papered fins when you're done if you're so inclined, but it's not really necessary, unless you just want the maximum strength you can possibly get...
I haven't had ANY problems with warpage in doing it this way, either... or paint for that matter...
Good luck! OL JR