How to use this for lash growth? Should this be applied on lashes or to the edge of the eye lid (lash roots)? Is it just one stroke or better with mascara wand?

Do not apply it directly on your lashes. You can do that with castor oil & it works wonders. But for this specific product you use it like an eye liner. Apply it on your lash line. Never use a mascara wand, if they wanted you to use the product like that it would be a wand and not a thin brush