I just moved up to a bigger tank 2 weeks ago and rinsed mine with the used salt water *(not fresh because that will kill the baceteria) until it ran clear.
I would scoop some sand in a medium sized bowl then pour in water shake like you are trying to find gold LOL and pour off the water, do this a few times for each scoop
I didnt have any ammonia spike with my change so I guess I did something right :)