Soaking the meat in fresh water is typically done with something like corned beef or country ham to pull out some salt. It's not necessary with a brine pork loin.
But... Before you go and brine, make sure that the pork isn't enhanced (injected with a salt water solution). It's very hard to find pork that isn't enhanced around here.
If it's not enhanced, here is what I use for pork...
1/2 cup Morton Kosher Salt
1/2 cup brown sugar
1/4 cup soy salt or worcestershire
2-3 T of whatever tub I am going to use on the outside.
1 gallon cold water
I mix it all up and heat to just under boiling and then let it cool and strain out any bits from the rub. Then I brine for one hour per pound (in the fridge). Then I rinse and dry and let it rest for at least an hour to equalize.