For the pony o's you have to remove the shank with a needle nose pliers. Yes it's a pain in the rump but it produces the best results.
Remove the shank, put the pony onto the shank and then replace the shank. After a few pony o's it will become easier. If you do it this way your button will be free to slide so no matter how your customer puts it in their hair, the button will always be able to slide to the top. If you just loop the pony o onto the shank then that means that the button can't slide and depending how the customer puts it on, it may be upside down. As for the buttons on the snap clips, I simply remove the shank altogether and throw it away. I then attach the button to the snap with E6000. Let it set somewhere where it won't be disturbed for at least 24 hours (preferably 48) and it will be all set. My middle daughter loves the snaps and my oldest is a fan of the button pony's.