"He who marches out of step hears another drum." ~ Ken Kesey
If your looking for a vintage look and a very soft print then yes, your leaving out so much info so that's about all I can tell you. I can tell you water color inks do a great job on light colors shirt's without an underbase.
You can really print it in whatever. We stick to either 180s or 225s, so you should be good with either of those.
For vintage style, 230 standard mesh should work great. Since you said gray ink, keep in mind that if you're printing on black, & you use only 1 pass, white will look grey. Maybe not the grey you want, but this white will definitely take on the tint of the garment underneath.