IMO mix the salt throughly for 24 hours or so...get it to an adequate temperature and keep it constantly circulating with a PH...first pointed towards the bottom of your container (or tank since it is your initial mix) to dissolve all the salt that will settle there and then towards the top so you can promote aeration throughout the saltwater mix.
That way you can ensure that the S.G. and temperature are within acceptable parameters so that you can avoid a huge shock and preserve most of the life within your LR.