I've used a number of brands but usually stay with one I like for years at a time. Two brands I liked: Red Sea's Pro Reef & Kent's Sea Salt. From 2011 to 2014, I've used Sybon's Reef Formula.
Due to space constraints, I need to buy bagged salt instead of by the bucket. It takes six bags to mix up 250g of saltwater at a time.
The external pump mixes up and keeps the saltwater in circulation until needed. Since the container is in the fishroom, the water temperature is close enough to the reef's temperature that water changes are easy. Opening a valve feeds new saltwater into the sump.
In 2015, I began using Aquavitro's Salinity. It comes in a large barrel (pictured at the top of this page) - basically a year's supply. Here's my initial blog: http://www.reefaddicts.com/entry.php/29230-Trying-out-Salinity-salt-for-the-first-time
Also, I use a digital Refractometer to measure the salinity of the water. Here's my review: http://www.reefaddicts.com/content.php/384-Product-Review-Milwaukee-Digital-Refractometer