Hi Cardimon,
I personally like the waxed variety.
If you want to tie it, try something called a waterknot. Used by climbers and cavers for webbing. I also use it for artificial sinew in doing reinactments. The floss will break before the knot does. You can probably find a better description in a knot book somewhere, but it's basically a single half hitch in one end with the other end following backwards through the first half hitch. It can be done with a figure 8 also. It holds totally secure for flat type string and webbing.
I've been using sewing bobbins for most of my string type "things", ie. fishing line, wire, floss. Get the metal ones...a little heavier but won't break. 4 for $1.35 such a deal!