This is the way I used to balance my "spare wheels" when mounting new tires. I used a long bolt with a nut, a couple of conical washers and a few pieces of ½" copper pipe. I use stick on weights that come in 1/4 oz sizes.
I just use my jack stands and carefully place the bolt thu the center of the wheel. Sometimes I use duct tape to hold the bolt and nut in place on the jack stands. I hand tighten the nut and bolt to snug the conical washer against the bearing inner race. This way it allows the wheel to rotate normally on the bearings. NOTE* If you have just installed new bearings, use a heat gun or hair dryer to warm up the bearing/axle assembly. It makes the wheel rotate easier for more precise balancing. When I find the heavy spot I tape some weight to the opposite side. I start with 1/2 ounce of weight and work upward. When I get it right, them I stick the weights to the rim, placing half the wieghts on each side of the center line.
Here is a link to a page showing a new way I have to balance my wheels. I got the idea from a picture I'd seen somewhere.