Here is an old trick that (surprisingly) not a lot of guys I’ve spoken to recently know about! If you’re on that shoestring budget, perhaps this could be an easy solution until you make your first million. Or at least a few extra hundred to acquire a proper follow focus lol.
The Silicone jar opener will have some flex in the design that might not be very accurate with your pulls, so another option is the Sunwayfoto Zoom / Focus lever. This lever is available in a few different sizes depending on the diameter of your lens, but also yields for a more professional look if that’s something you have to worry about. They are available on both Amazon (click here) and on eBay (click here for SunwayFoto levers).
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SunwayFoto Adjustable Zoom Focus Levers