You didn't say what kind of tent it is. I don't mean to insult your intelligence, but make sure the tent is made of silnylon. Silnet won't work on regular PU coated nylon...use Seam Grip or similar for that.

I'd pitch it, thin the sealer with mineral spirits, apply with foam brush a little beyond the seams. If you do it out in the sun, it won't take long to dry. I've never had to use the talc, but there are some variables, so you might. I'd seal on the outside of silnylon. I've never done a silnylon floor...maybe inside would be better there. It probably doesn't matter too much.

If you have a scrap of silnylon, you could mix a small amount of sealer and practice, at the same time getting a feel for the right sealer-to-thinner ratio.

For urethane coated nylon, though, seal on the coated side, which is usually the inside. No need to thin Seam Grip, although you could thin it with toluene (avoid breathing the vapors.)