Solvent-based Nitrocellulose lacquer has been the dominant finish used by cabinetmakers when finishing high-volume furniture manufacturing as well as when makig guitars. Nearly all steel string instruments made since the 1920's are finished in lacquer.
This finishing material is made of nitrocellulose combined with other resins (to promote flexibility, durability, etc.) dissolved in lacquer thinner solvent. The lacquer film forms and cures as the solvent evaporates.
Two-Pack is called just that because the hardener needs to be mixed to activate the lacquer. It is a better quality, more durable finish with the hardness and viscosity able to be controlled with slight variations in the lacquer/hardener mix. Must be thinned down with lacquer thinners once activated to spray finish.
Unlike standard polyurethane finishes, lacquer generally needs to be spray-applied and will no work being brushed on. If you require just small quantities of lacquer then the Mirotone (another well-regarded lacquer brand) make handy aerosol packs that are available here.
Please note that it is highly recommended tha all timber to lacquered should be pre-sealed with sanding sealer and all lacquers must be thinned down usually at a ratio of 50/50 or possibly even a higher mix of thinners for light top coats, with sanding of 240 - 320 grit between multiple coats.
The 400mL hardener will suit a 3.6L tin of lacquer.
This product is classified as a dangerous good by shipping companies so it is not available to order online and can only be purchased in-store.