Concrete mix

I believe there is also 4000 psi bag mix by quikcrete that is commonly available, might be a labor saver, by not having to deal with mixing portland and various aggegates, sand and crushed stone from scratch etc.

You're not alone on forgetting the hand mix ratio's, I do the same thing, don't do it enough I suppose. One thing to keep in mind, make sure when you mix it, that all the materials are uniformly measured including water, don't have to be precise, but to achieve the strength needed, it does play an important role if you keep the amounts reasonably uniform to the designe mix used. Water/Cement ratio, that is where most mistakes are made, too much water will negate what the bonding agent does, (portland cement) and will weaken its compressive strength drastically.