Since you found already your perfect epoxy from the perfect supplier you have it in front of you and the technical data sheet beside you - there you find the mixing ratio - be careful in the difference between "mix by volume"  or "mix by weight". Get your plunger , measuring cup and your wife's kitchen scale ! Big and heavy container are mostly a nightmare if you just need to mix 4 or 6 oz - try to refill in more handy container - 1 gal size is a lot easier to handle and you waste less.
My idea is to fill first the Resin and after that the hardener - if you got too much - you can fill to the next mark to get an equal mix - and it is better to have a bit ( don't get me wrong on the bit - I mean max. 5% with bit ) more hardener than resin. Double check on the scale if the relation fits - after that, pour the whole stuff in a handy mixing pot - something which lays good in your hand and has no corners on the floor. Mix it well through! Rule of thumb would be 1 minute for each 2 oz (50 ccm in metric).
Why so long ....?

Get your two glasses of different honey ( to make this example easier , get a light and a very dark one)- take a fresh mixing pot and try to measure correct - you will see it is not as easy to get to the mark as you thought - now if you have the honey mix, pour it in a glass where you can look through
Write down the time. Get the mixing stick and start mixing the honey. Mix till you see no more lines in the honey from one or the other kind. Don't forget the edges at the bottom of the glass and you will see how long it will take you to get all mixed well. If you are done, take one more look at your watch. It will take even longer to mix your resin.

My Resin is too hard to pour!

As lower the temperature as harder your resin gets. Look if your temperature is still okay to apply your resin. If you just stored the resin on a too cold place - like concrete floor - you can set your container in warm water ( 100 F / 35 C). Don't take too hot water since it will speed up your Epoxies reaction and shorten pot live. It will take quite a while to get more fluid. Here your resin reacts as honey - as warmer it is, as more fluid it will get. If you keep this in mind ... you should have no problems.

Pot live !

In your technical data sheet you will find the pot live of your resin - 'Pot live' is the open time of the resin - how long you can play around before it starts to set - just this is a very relative time. You must read on in your data sheet for which amount this pot live is. As bigger your mix is as shorter gets your pot live and as warmer your workshop is as shorter is your pot live - somehow our supplier's don't write this together on the same line. And it might make you wonder, if you have a resin with 30 minuets pot live and mix 24 oz ( 700 ccm) and after 15 minuets you can boil eggs on your resin. Try to make small batches, not more than 12 oz ( 350 ccm ) to have enough time to mix it well and apply it without a rush. If you tell me now you have to laminate a 64' boat hull and it might take you a century with 12 oz cups - you are right - on big surfaces, you need one person just to mix and a second person to apply. If you have big batches, you can spread your resin right away after it was well mixed over the glass. The bigger surface is not allowing the resin to boil up and gives you more time to apply it.
It is a good idea to start on the tricky parts with the fresh mix - hold your mixing pot in the hand and let it not stay in the sun - if you feel it starts to get warmer, just spread the remaining batch over a big surface. So you can make the most out of the batch and the time. With time, you will get a good feeling for your resin! So please don't mix your 1 Gal. resin at once and wonder if after 10 minuets you reached the potlive of your mixing pot - which is smoking on the floor.