I went riding in some sandhills today and there were a few steep sections with deep loose sand. I had plenty of gearing to handle the incline, but when I stood up the back tire would spin out and if I kept the back wheel weighted enough to get traction, the front end would lift and I'd lose steering. I'm running as wide of a tire as the frameset allows though not an aggressive tread. I'm fairly new to offroad riding. Is there a technique for riding uphill in loose stuff or is it just a matter of more tire?

Thanks