2 Pack Grey Primer Set (2K)

2 Pack Grey Primer
Pack Contents :

• 1 x 100ml Primer (High Build)  also known as Urethane or Polyurethane (Supplied in Glass Bottle)
• 1 x 30ml Hardener (Supplied in Glass Bottle)
• 1 x 60ml Thinners (Supplied in Glass Bottle)
• Instructions

Mixing Ratio
4 Parts  Primer + 1 Part Hardener + 10-30% Thinners,
e.g. 40ml  Clear, 10ml Hardener + 15ml Thinners

ONLY MIX WHAT YOU NEED EACH TIME, once it's mixed it has a life of about 15/20 mins max then it has to be discarded.

Is it possible to pre-mix your 2 pack Primer then keep it in a jar for later use if not all used in one go, or is it a case of just mixing enough to do the job?

NO YOU MUST NOT DO THIS, once you mix the primer and hardener a chemical reaction is started, similar to epoxy glue or epoxy putty. It will hardened within 15/20 mins, if you mixed the lot you would be wasting product and money, so only mix whet you need each time, you will quickly find the amounts you need with a small amount of practice. 
What do I clean my Airbrush and equipment with after use