There are many ways to measure and mix epoxies.

I've always had good luck using pumps. Yes, pumps have issues. Every system does. You figure it out and work with it.

Pumps have a column of liquid pulled up the pump and held with a ball bearing. Over time epoxy resin, more so than the hardeners seeps down past the bearing. So, if you haven't used the pump for a while, when you press the pump you'll likely to have air come out first, instead of a full stroke of liquid.

Solution - Always assume there will be air in the column and press the pump down slowly until you feel the firm pressure which tells you the air is gone. Then release the pump and let it rise to the top of the stroke and you're ready for a full measure.

Typically when I'm using pumps often I don't have air but I just have the habit of pressing down slowly so I'm ready for trouble. If I have a burp of air in the middle of a stroke, which sometimes happens when changing pumps, I add a little extra to make up.

If the mix is ever off, and I know it, like I forgot to keep track of strokes, just pitch it, it's not worth the headache.

To do some very small batches. I measure the pumps stroke and carve a notch and mark with a marker halves, quarters, and eights. Works for me. I use only 2:1 epoxy.

I do find MAS epoxy tends to crystalize in the pump spouts if left for long periods. I use MAS for speed and System Three for transparency.

Graduated mixing cups are available too. Pouring and dripping epoxy is not what I like to do.

I set my pumps in a box of kitty litter to catch the inevitable drips.