When I make poultry brine, I make it in two parts -
1 - Water, Salt, Sugar - all cold, I just stir to dissolve
2 - 1 c. water and all my whole spices
I boil the 1c. water (with the whole spices - garlic, ginger, allspice, cloves, cinnamon, etc. - whatever I've got) into a "tea" then add it to the bulk of the brine. That way I don't have to mess around with boiling the whole thing, then getting it cooled down so I can add the meat. As long as the salt/sugar dissolves, you shouldn't NEED to boil it.