Before they had non-blush, I used to mix the fast with the slow hardener 1:1` and that gave me a good working time but an overnight basic cure. First time I used the slow, I thought I screwed up and it wasn't going to cure.

But the fast epoxy does blush so be cautious of that. I always liked the Non-blush a lot. Fast enough but plenty or working time. So, you can always buy some fast cure hardener and mix it with your hardener. Just remember its still 2-1 epoxy and your are just mixing hardeners.

Plus, always remember to mix throughly by scraping the bottom of the mixing container, along the sides etc. You can get a soft spot if your mix is not totally homogenized.

I just make sure I use a fine blade when cutting out shapes in glassed areas. Sometimes I make multiple passes with a utility knife first but be careful your blade doesn't travel off course. The old matt cutting trick: one light path first and then travel in that groove.