I just leveled this char in about 2 days played time with a few hours of it being afk in cities.What I did was run every single dungeon one time and do quests while waiting in queue.That way you don't get bored and the experience gain is great.Works particularly good between 60 and 90. WoD is a piece of cake if you just have flying and Legion is questing + doing the per zone dungeon for the 100k xp quest.
Determine the gear stats and armor type you need for your new character. For example, a paladin requires Strength as their main stat, and heavy armor (the armor type) will scale as the character scales if they are initially unable to wear heavy armor due to being a lower level. Your optimal heirloom gear set will feature the same main stat as your starting gear.
If you're looking for simple, just get actionator. Set it to undercut everything you post for 1c and alt click from your bags. It will place the item on the ah window, do a scan for that item and autoset the price for how much you told to undercut (you can change it accordingly if you feel like it). It will remember if you do stacks for which items and replicate it everytime.