Help - Barre with pinky?

Thanks to suggestions in this group, I am learning from Faster, Cleaner, Better by Aaron O'Rourke. The exercises are really helpful!  But I'm getting stuck/frustrated with the 'pinky barre' exercise. Is there a trick to learning how to do this?  My pinky finger is small and seems even smaller and weaker when trying to do this!  Any suggestions?  Thanks so much!