Sure. I've used both Quik-jet and Arborjet systems. The Arborjet has been mainly Tree-age injections for emerald ash borer, and I've also used it to inject Lepitect ( acephate) for obscure scale in oaks. The Quik-jet has been miticides, insecticides and fungicides on various species. Both use the Stinger injector along with tree plugs which are inserted into the root flare( amount varies based on dbh). The plugs have a rubber stopper prevents liquid from entering or exiting the hole once fitted. You use the supplied bit to drill the holes about an inch or so, then tap the plug into place. Place the stinger IVs into the plugs, pump up the pressure and release the valve, and the liquid starts flowing into the tree. Uptake is usually fast but is dependent on species, condition, size, and the weather. The quick jet is the same but you simply pull the trigger on the gun to give it a calibrated dose per injection site.
Pros: less mess, no need to spray, no motorized equipment, no huge bulk of chemicals, no mixing of chemicals. Good way to get product into tree and treatment can last several years.
Cons : plugs are expensive at a dollar each. Can be unsightly on high profile trees and on smaller trees you are limited to how many injections you can do cleanly in its lifetime. Severly stressed trees are not good candidates for this as uptake may not be as good. There can be lots of little pieces it break or lose. Rubber gaskets an o rings blow out and parts kits are PRICEY.