Since its something you are going to have to do fairly regular, you might invest in a worming bit. They aren't too much, less the $20 I think. I use one for a hard to worm mare. I got tired of wasting the paste. They work great but do take a little more time since you have to leave it in the mouth for 5-10 min. Before removing it.
Heres one http://www.drsfostersmith.com/produc...m?pcatid=16163
They may be cheaper elsewhere but Fosters and Smith is a good safe internet company.