It also needs to be remembered Gaara has always been protected, whether he wanted it or not, autonomously by the bijuu chakra. So, I think he didn't especially need to learn to tap into that power (though he needed to develop techniques of course) nor did he need to be under tremendous stress like Naruto was under Haku's bloodline limit jutsu. That also suggests the sealing used to trap Shukaku inside Gaara left the beast much closer to the surface, for good and for bad.