Tying is very easy! And fun, and soothing, because it is easy and repetitive. Here's how I do it:
First, clear off a table which does not have a surface that you care if it gets scratched a little. Spread the sandwiched quilt over the table and pull up a chair.
I use a curved upholstery needle with a big eye. I use Perle cotton. You can use a nice long length. Figure out how far apart the ties need to be, based on what the batting says about the quilting distance.
Thread the needle, but don't knot it. With the upholstery needle, go from the up side to the down side. Leave a tail on the up side of about 3 inches. Go from the up side to the down side again in the same place. Tug a little to tighten up that spot. Without cutting the thread, find the next spot for a tie. Go from the up side to the down side twice, just like you did before. And repeat. When you reach the end of that length of thread, go back and tie them off: Cut the inbetween lengths. Tie two surgeon's knots in each spot: Right over left and around twice, tug tight, left over right and around twice, tug tight. Cut thread tails off at one to three inches, depending on the effect you want.
If this doesn't make sense, let me know!