ash is like oak so the same applies. if you want a light stain, like a honey color. i'd use thinned coat of blo 50/50 (blo/ms), flood it, let it soak in for about 20-30min keeping it wet, then meticulously wipe it dry and keep doing this for the next day or 2 cause it'll seep. let it dry for several days. then follow with any wiping varnish. The blo will really enhance the grain and will leave a nice warm honey color. i don't like to fill the grain but that's just my preference
if you want a darker stain, then you'll definitely need a wash coat first otherwise it'll be blotchy. alternatively gel stains are generally pretty easy to do as they don't tend to be blotchy. then follow with any topcoat varnish.
Sam