Oil only on one side of engine... help?

Easy stuff first. Have somebody help you so they can turn the engine over slowly while you prime. You may have simply passed the sweet spot for the oil passage to the drivers side. If that doesn't work I would take off the drivers side rocker shaft to make sure it is installed correctly, or otherwise verify it isn't the cause of the problem, that is, is it a new rocker shaft or old? If it is a used one, did you clean it? They can get sludged up. The shafts have cup plugs on either end you can remove to clean the insides.
I don't think sticking something down the oil passage to the cam will help...it would be hard to tell if you hit the cam or the cam bearing (if the bearing is rotated wrong).