I typically don't grind -- usually just battling trainers will suffice until I hit the E4, where I might have to gain a few more levels in Victory Road. Chances are I will probably have to do this in HG as well. Can't tell you if I will, though, because I'm nowhere near 8 badges yet.
However, my team is set up so badly in terms of Special Defense, that Morty's Gengar messed up my team. Seriously, hardly any of them could take one Shadow Ball, let alone more. So I was stuck grinding outside Olivine for the past day and a half, with Pokemon 5-9 levels lower than I was. And I still only beat him by sheer luck. :(
I hate grinding in Pokemon, so much. It gets boring after awhile, and I just want to move on.