It just takes time and patience. If you are re-using pieces then it takes a little longer so you don't damage/break anything when you take it apart (specifically the hog ring loops).

 

In the four seats I've done, it's easiest to just plan on using new hog rings. It's also worth buying a real set of hog ring pliers instead of the really cheapo unit which comes with the seat covers. The Seat Shop supplies all the hog rings you'll need. Just cut the existing ones off and hook in the new ones... not hard at all. Just make sure that you get the seat cover's outer seams lined up well with the foam edges before you start pinching the new rings onto the seat foam.

 

Definitely get a real set of hog ring pliers. I bought the ones from the Seat Shop for a few dollars and that's what they were worth. They worked but were painful with bare hands (no grips on the pliers). If you don't want to spend an extra $10-$15 for a good pair I recommend using some gloves to save the day or two of sore/tender hands.

As for the hog rings I cut the old ones off and bought a bag from the Seat Shop to make sure I had enough (in case I messed up in the beginning and had to start over). With my seat being 15 years old with countless hours of a butt sitting in it the foam was not nearly as resilient as it used to be. Even though I wasn't being careless during the removal process some of the loops did rip off the seat. Not a big deal for me since I was installing new pads but something to think about if you're going to refresh and re-use them.