I paint the axles before mounting the wheels. I painted them with a brush for a long time. Brushing almost always needed at least to coats. Metallic paints were the worst. When applying the first coat of metallic paint, the color would soak in rapidly, leaving the metallics on the surface. Nowadays, I dip the ends of the axels in a couple of drops of paint. I touch the end of the axel to the paint and holds it there for a couple of seconds. Holding the axel in the paint for a short time lets the end grain soak up as much paint as it can. So far, this has been very successful and never requires a second coat of paint. You need to dip the axel just enough to cover the entire end with a tiny bit of overlap. It the wheels fit snug, this extra paint will get scraped off by the wheels. I usually let the paint dry overnight. I hand fit each axel to the car body.
Rounding the axel ends is a bit hard to explain. I do it by hand using a sanding block and 80 grit sandpaper. While holding the sanding block in my left hand, I grip the dowel in my right hand 90 degrees to the surface of the sanding block and moving it in a circle. The dowel will wobble in your hand as you sand and produce the rounded end. The tighter you grip the dowel, the flatter the end will be. I like to rotate the dowel in my grip a quarter turn every few loops to keep the shape uniform.
To get the axels to fit correctly, I hand fit each pair of axles. To do this, I put a wheel on the dowel followed by two nylon washers, the car body, two more washers, and another wheel. I press everything down tight on a flat surface and mark the axel length. I disassembled the toy and cut the axel to length using a 20 TPI Japanese pull saw or flush cutting saw. I then sand the axel ends to shape and paint them. When the car is assembled, I only use one washer per wheel. I use the second washer to add just enough axel length to allow for rounding the ends.
I use Tightbond II to glue the wheels on. It holds tight and gives me enough working time to position the wheels. I put the first wheel on the axel, aligning it carefully, so it is in perfect alignment. I set this assembly aside until the glue has cured. I learned the hard way not to try to position both wheels at the same time. After the glue has cured, I insert the axel in the car body with washers and glue the opposite wheel in place.
When gluing the second wheel in place, I insert a plastic spacer between the wheels and the body. I press the wheel on using a vice with leather padded jaws. The wheel is pressed on until the axel just protrudes into the leather. The spacer is there to make sure I have enough clearance for the wheels to turn smoothly. If I did everything right, the hubs will protrude just a bit past the wheel and look like a tiny hubcap. Remember baby moon hubcaps.
