Pick up a quart of actual 2 stroke oil, that makes a difference too.
I use synthetic 2 stroke oil, but I have several 2 stroke engines. In addition to 2 weed whips, I've got to keep a chainsaw, a leafblower and 2 sleds running.
Another trick is to pre measure the oil and have it at the ready in their own little single serve containers, say for 1 gal batches at a time.
50:1 requires 2.56 oz. of oil per gal. of gas.
40:1 requires 3.2 oz. of oil per gal. of gas.
So you can see how easy it is to throw that ratio way, way off.