As mentioned by others, letting the heat gun warm up for 30 seconds or so before directing it onto the paper really cuts down on the time needed to melt the embossing powder (and less time to fry the cardstock!)
I discovered years ago that the way the paper is held while heat embossing can cause the cs to have curves on the edges. Anytime I hold the piece in my opposite hand while heat embossing the edges get warped.
To avoid this, I covered a small clipboard that is made from particle board with aluminum foil and use this as my holding board for anything I heat emboss. It is easy to catch a tiny edge of the paper piece being embossed under the metal clip so it doesn’t fly away, and i don’t burn my fingers. The foil will take on some heat while you are using the heat gun and helps melt the embossing powder from the back.
This combination of having the piece being embossed held in a flat position and the added gentle heat from the backside helps minimize the curling/warping on the edges. :cool:
If by chance you want to try this, the small particle board clipboards (fit 5x7 pads) are available at office supply stores and sometimes Walmart (under $2). Avoid using a plastic clipboard because they might melt and definitely wont maintain the heat like the partlcle board does. Then take a piece of aluminum foil and cover the front of the board (including under the clip) and take the excess foil to the back and crimp in place. It will stay like that without tape. It will last for years without needing replacing. The clipboard clip has a hole in it so it can be easily hung on a hook near your heat tool for easy access.
I got this tip from someone on SCS well over a decade ago and I am still using the same clipboard and the original foil!!!