I added another layer and drew in some small whiskers around his mouth using the pencil tool on 50% pressure and Softness and 25% size with Precise set to on...

(nearly finished)
Then I added some whispy hairs to the edge of his fur with the pencil tool and softened them with the new blend tool so they were not so harsh.
For his large whiskers I added another layer and set the opacity to about 59%. Then using the paintbrush set to 7% size and 8% pressure and 30% loading I painted his large whiskers. I used an off white colour sort of a blue-grey. I still found the large whiskers a bit harsh so I went over tham with the eraser set to a very low setting.
There you have it I hope I explained it all OK. If there is any part that I didn't explain very well....just let me know and I will be happy to try and help