This is a tip for the the DIY people not the trades that know other ways or use a whole bag at a time.
If you are a DIY person doing a bit of plastering and just bought a large 25KG bag of whatever (Finish, Bonding or Browning)
But will not use the whole bag, possibly only a small part of it.
and have read the instructions on the mix ratios and have all clean tools to hand other than a way to measure it all out.
Kitchen Scales is one way to go
A plastic milk container (the kind you get from any supermarket or corner store)
From 1L to 2L is very useful. (you need 2 cut to the same size)
Just use a sharp knife or scissors to cut the base of as close to the leading edge for a full size cut or to the already marked
gauge stamped along the side of the milk bottle for a smaller scoop.
Make sure both are cut to the same size (there is a little give and take here, but get as close to the same size as you can)
Then allow to dry or wipe dry with kitchen roll or loo roll (if loo roll, tap / shake out any bits)
Just stand the bag of whatever plastering product you bought against a straight wall, cut the bag along the top
and loosen it up with your trowel and then dig in with one of your new home made scoops, level of with.
your trowel and dump in your mixing bucket.
Repeat it as needed for the mix to water ratio required.
Use the other similar sized scoop to add the water. Keeping dry product and water separate.
If it was not obvious before, you need to keep the screw cap on the bottles at all times after cutting the base off.
Just a little tip, probably mentioned before, but just discovered by me as necessity drives invention.