Previously, there have been 2 ways to inject the wash material around the preparations. You could use a traditional single-chambered intraoral syringe into which you’d have to place the already-mixed wash material. So, you mix it, put it in the syringe, and use it immediately and you and your assistant do your best getting your timing right with loading the tray material. Both reusable and disposable versions of the single-chambered intraoral syringe have been around for a long time.
As our profession has evolved from amalgam to composite for posterior direct restorations, one of the biggest clinical challenges has been creating consistently good proximal contacts. A number of gizmos have come through the marketplace promising to solve this vexing issue. I've tried a number of them with varying results.
In the past, chairside reline materials left out a lot to be desired—they were messy, they were smelly, they stung the tissues, they tasted bad, they were very exothermic and could even burn the soft tissues, and the result was always less than satisfactory. The old chairside reline materials tended to delaminate and stain, too. Basically, they sucked. But, they were better than nothing for those patients who simply would not relinquish their dentures for any amount of time.