I've always been a borderline grinder, but am continually trying to move towards spinner. My thigh muscles are over-developed compared to the calves, although the latter have improved over the last several years. I've found changing my cadence to be difficult. I don't know if that's just me, though. Perhaps I'm just not trying hard enough to change my pedaling technique.
I noticed something interesting on one my more recent climbs up a mountain east of Melbourne: I've been up it on at least half a dozen occasions now, and it typically takes me 90 minutes to ascend. I was in the habit of using 39/16 gearing (a triple crankset on a touring bike). On this occasion, though, I decided to use 39/18 (i.e. middle cog on both front and rear), and to my surprise ascended the mountain in exactly 90 minutes as before, but with legs feeling more refreshed. So yes, I really must move more towards spinning.