I hate to be the bearer of bad news, but 1 speed people can be just fine. As an owner, if you supply the tools (aka iron), 1 speed people get a ton done. Of course you can work on their efficiency of movement, which imo is where speed comes from at work in the first place. Working smarter not harder. Minimizing wasted movements that don't add to production. Expecting non owners who are paid a flat hourly rate to completely bust their ass continuously for your profit is honestly an insane expectation.