A few years ago PR1422 was withdrawn as it was deemed to be hazardous. I don't know what the hazard was but take care if this is what you have and use gloves as it is very hard to remove from the skin.
When I started in this game it was PR1422 and PR1422BT (Brushing Thickness) then it changed to PR1422A for the runny stuff and PR1422B for the thick stuff.
MEK is available mail order on ebay.
Mix MEK with the base sealant and then add the activator. As eric says, do a test batch.