Either a box and a mason's hoe, or buy a mixer. I got a decent used one
for $50 and $10 or so in gas money via craigslist - otherwise the
new/plastic jobbies are pretty cheap new (and pretty cheap, in the "not
to be confused with inexpensive" sense, but probably more reliable than
whatever silliness you are contemplating with a 55 gallon drum.)

The box and hoe can be quite effective if you learn to use them
correctly.

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Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.