weight it out in some kitchen scales then put it into your hand and you'll know.
Once you've sprinkled it, give it a little tickle over with a hoe to get it below the surface and let the moisture start to work on it.
I use an old yoghurt pot or cream carton - weigh the right amount out and mark the level on the carton with a felt tip pen. Then you can use it as a scoop
I've never really measured what I put on hollie
I'd reckon a scant handful should cover a two or three square feet I think.
I have quite small hands....