Stuart,
I'm certain you know how to use 5-minute epoxy so please pardon my rambling. I'm 62 and have been using it since I was 15-years old. Mostly on balsa planes way back then.
Here's what I've learned. Pay the extra money for a good brand epoxy at a hobby store. Not the newest brands from the big hardware stores.
1) Prep the areas to mate by removing paint/chrome etc. Rough/scratch up the surface with coarse sand paper or the back of a hobby knife.
2) Make sure that the mix of A and B are as equal as possible.
3) Doesn't matter what the instructions say. You have one minute to mix it so make it fast. You want to work with it while it's thin (thick epoxy strings like crazy). Stir it quickly with a popsicle stick. Then squeegie it to one side and stir again. Repeat several times until the glue is slightly milky white without any totally clear areas. Hit a timer when you start mixing so you actually know. Make sure to mix the glue on poster grade super shiny paper or cardboard, or the paper drinks the thin part of the glue and it thickens up fast. I cut up and use thick shiny brochures.
4) Choose the right applicator. Body posts are okay with popsicle sticks. However, windows, bumpers, and finely detailed parts require these microbrushes. They come in various sizes. I have boxes of them. Cheap insurance when you consider they help prevent build/wreckage.
One last thing. Don't apply glue with the mixing stick. It's tainted. Set it aside and apply the mixed glue to the car with a clean new stick.
I was the first person in my club to epoxy motors into scratch built chassis back in 2018. Everyone thought I was nuts. Today almost everyone in the club epoxies their motors in. Who knew?
Good luck!
Ken