Masking with custom fonts?

I’m trying to create a simple shine across some of my custom text but for some reason you cannot duplicate the custom font and use it as a mask it just doesn’t work. The only option it seems it to paint around the text i have in order to be able to use the mask. Is there an easier way around this problem?

My layers would look like this

>Duplicated custom font ( mask applied )
>Shine animation
>Custom font

It works fine when i use standard fonts. can anyone help?

thanks in advance!

Tris