I have always used West System Epoxy. i found it incredibly reliable in its accuracy. They have charts that show set-up time for each type of epoxy under different temperatures. You can set your clock by it.
When I had my commercial shops, I bought it by the 5 gal kits. When using it just for personal use, I bought the 1 gal kits. The more you use it, the more you will find other uses for it.
They have thickeners for different uses. Some are to make it a stronger mix, almost like putting gravel in cement to make concrete. Other thickeners are used with the epoxy where filling gaps are easy-sanding are more important than strength. These type fillers are used alot in boat and other fiberglass repairs.
Most of all, their customer service and tech support is excellent At least they used to be haven't used those guys in years.
Tony B Retired woodworker, among other things.
"Strive for excellence and settle for completion" Tony B