Brining will help with moisture - without question.
BUT....an equal issue of how it pulls - is as much about how the muscle tissue runs in any cut of meat. Loin is a L-O-N-G strand muscle. Think about the physiology of say...your bicep muscle ....it is connected via tendons to your shoulder on one end, and at the elbow joint of your arm, on the other end. The muscle fibers run lengthwise. Just like in a loin.
Butts pull so well because in this cut of meat, the groups of muscle fibers run in a number of directions, and not for much distance. As well - there is plenty of fat and connective tissues which constant melt and bathe the muscle fibers as we cook the butt - tenderizing it.
SO: You may find that after cooking the loin, if you slice it - across it's length ( which is also across the "grain" i.e. - @ 90 degrees to the length) in approximate 3-4" sections, then try to "pull" the sections - you might get a very lean...likely in need of added moisture via saucing - but really tasty "pulled pork".
Some folks really prefer leaner pork anyway...we will keep them in our prayers......