do you have a pic of the swyer meterThe simplest chem injection is one where the pressure pump will self-prime using a Dwyer meter before the pump. Cat pumps are the best for this, but any pressure pump that self primes will work.
The pump pulls from the fresh tank and chem jug at the same time, and the adjustment is an inline valve which feeds the pump from the fresh tank, or water box. Once you get it set while keying the wand, then you can use the calibrated markings on the Dwyer to adjust chem feed - pretty much nothing to wear out and will always work great!
I have been using this setup for over 30 years with no problems.