It absolutely does matter. If you mix too much alcohol of either type (regardless of the percentage) it will make a soupy mess that will never set properly and will remain soft and gummy for the life of the model. While it's possible to thin epoxy with alcohol and have no problems, it can also be a mess if you mix too much alcohol in. As I said, it will never setup properly. The problem is that you are not just thinning the epoxy. The alcohol actually changes the chemical structure of the epoxy components, and too much will keep it from setting properly. I've had one time that this happened to me, and it too me hours to scrape all of the epoxy off in order to start again. Since then I have thinned epoxy with heat. Use 30-minute (or higher) epoxy and put a small dab of it on the area you want to fuel-proof. Hit it with your heat gun and it will thin out to the consitency of water. Use a disposable brush to cover the area you are working. Just know that the set time of the epoxy will be reduced as you heat it. I like doing it this was because the thinned epoxy wil seep into the pores of the wood and give you better protection.

Hope this helps

Ken