Was just posting about this in another thread
Put the gel (a very small amount) on the areas you're going to apply the minoxidil. Personally I wait about 20 minutes to allow the tretinoin to "do its thing" to the skin, and then apply minoxidil, but it probably doesn't matter that much. If you don't want to be in and out of the bathroom just try applying one right after the other
.1% is strong to be starting out with. If you want to use a percentage that high, it's better to build up to it. I use .025% and its very potent, and I probably won't be increasing the percentage
You want to be really gradual so your skin will adjust and you don't end up with a red, caked up scalp. I recommend starting out with just a couple applications a week, building up to EOD or ED (depending on how well you're tolerating it) over the course of a month or 2