Alternatively, for even faster grinding, in spinel town there's a trainer that offers to trade you a karrablast or shelmet for the opposite (i.e he will trade you karrablast if you trade him shelmet). You can get an accelgor or escavalier that gains faster exp due to being traded that way. Make sure if you pick accelgor that you can take down the tyrannitar, and if you pick escavalier, something to deal with sableye.