Believe it or not I like Texas Chert better than English flint for flint & steel. Last I bought was a 5 pound box off of ebay. Good stuff.
I don't like denim for char cloth. What I like is old worn out torn up carhartt shirts, coincidentally the same material I use for patches in my flintlock. 100% cotton, just the right thickness, easy to make char cloth with, and a great way to repurpose a formerly expensive shirt instead of just tossing it. I kind of look forward to the next one I "ruin".
As far as "a few red glows" on the char cloth. It's not going to flare up. That little glow is all you get. When you blow ever so gently on it it will travel across the char cloth and consume it. Literally, all you need is one single spark to catch and get that tiny glow going. Your job is to see it happening (do it in a shady or dark place because strong sunlight doesn't let you see what's happening very well), then place the char cloth in your tinder nest, and blow gently until there's enough heat produced to light the tinder nest. Think ahead and have everything ready to go and in reach.
It does takes a knack and some finesse but once it clicks for you it's one of the easiest woodcraft jobs there is.