When I made my cinnamon swirl brioche, I made 2 loaves so that we could have some french toast with the second loaf. And I know, I keep saying I'm trying to lose weight and eating brioche is probably the stupidest thing I could be doing to reach that goal ... But it was a special weekend and I'll run it off this week. Hopefully;)
If you're making French toast with a delicate sweet bread like brioche or challah, I recommend the America's Test Kitchen method, which is to toast the bread first. I just put the slices on a cookie sheet, stuck them in a 250° F oven for a while until they got dried out and just barely crispy. Flip them over, and do the same on the second side. This worked out well because last time I tried to make French toast with brioche, the slices had a hard time holding up in the custard. But these guys did awesome! And they soaked in the custard perfectly and it was delightful. I was a good girl, though, I only had one slice.
As for the custard, I think everyone has their own family/individual recipe. I'd never made french toast until I was married (because it's my husband's absolute favorite) so I had to figure out a recipe I liked. And I LOVE it. What do you like to put into your custard? Cinnamon? Vanilla? Nutmeg? What's your egg:milk ratio? Do you sweeten it? Tell me, tell me! I'd love to know how other people do it.