I use Satin Cream by Vellus Products which can be obtained from Hub International their website is
www.hubint.com and this has been very helpful in increasing the growth of the moustache on my two yorkies. You can actually use it on all the coat to help growth and although it seems thick it does absorb into the coat very easily and washes out easily, it just looks a bit greasy at the time but if the coat is wrapped in papers you will not even notice it.