model car paint at wal mart is a buck or two. they have oil and water based paint you can buy. either one cleans up well and if you screw up, you can completely remove it. i use a tooth pick because while dabbing it in the paint it is easily "worked" into the crevices. it doesn have a tendency to "fill" and even out in the crevices. as far as a steady hand - if you use the tooth pick, it'll naturally follow the crevices as long as you don't overload the tip with paint. all in all, it works pretty slick.
here is a
link to a post i made. you can kind of see the color i'm speaking of. i wouldn't hesitate to use this method. the crayola affair is fine too.
i do see more merit in the paint, simply because of finished appearance, ease of application, and the infinite color choice. with paint, you can mix and match any color you want....
hope this helps.
septic tank