I fuse alot of bottles and always use devit spray, I actually apply it with a small paint brush. It makes the bottles very shiny and pretty, totally elemniates devitrification. only use it on the part of the bottle that is facing up. Don’t put it on the part of the bottle that sits on the shelf. I usually wipe the sides down alittle to be sure it is clean. If you play with it you will figure out how to best apply it for the best outcomes.
Also, you might want to experiment with lower temps for other looks. The higher temp gives a smoother look but they are also nice for trays with lower tempatures. I like the full fuse for decorating and lower fusing for serving trays.