Thats how I done my 55.I put the dry in first then the live.
The way I rinsed mine was using a big mixing bowl,I filled the bowl about a half to 3/4 full and let water from the outside fosset run through it untill the run off water was clear.After I got each bowl full rinsed I used my wifes hair dryer and dryed the sand out while stirring it.After it was fairly dry I slowly poured it into the tank.
It clouded the water for about a day,but that went away pretty quick.After the water cleared back up I laid the bag of live sand on top of the dry and cut the top off the bag and slowly worked it out.
It took me about 2 1/2 to 3 hours to do it that way,But it was worth it.