I use a very small punch, stick through the other hole, stretch it and try to get it to go back over the pin. Sometimes it takes a minute or so, but you eventually get it.
I agree the easiest way to get the pin in through the spring is to use a small punch or precision screwdriver from the opposite side that the pin goes in. You should be able to hook on to the edge of the spring and pull it to the center, so the pin slides through it. After a few tries, you will find this works quite well.