Can I use use eyeshadow applicator brushes instead to apply my Latisse?

Yes, if you can't use the original Latisse brushes then you can use a thin eye liner brush to apply Latisse. It will give more precision than a normal shadow brush.

I don't think that's a good idea. You want to be able to precisely control the amount of latisse applied and where. It's best to use the applicator brush that comes in the package or a very fine eyeliner brush but then make sure to clean it thoroughly after each use. Best, Dr. Nazarian

I suggest using the applicators that come with
Latisse. The recommended usage is one applicator per eye, but some of my
patients tell me that they use one for both eyes and then dispose of that
applicator. The issue with eyeshadow applicators is that they often have a
sponge tip that will absorb the product. That means less will go to the lash
bed and that may affect the results. Also, unless you are using a new eyeshadow
applicator with each use, it won’t be as sanitary.