Hi there!
There are different ways to paint heraldry.Some of the drowings are easy,like crosses,and some are more complicated,like the typical animal heraldry.
On the more complicated:
1-If you want to use a guide(like the outline you described...)don't do it using graphite!Instead of painting the heraldry on normal paper,do it on a sticker.Apply the sticker and remove it when you'll be READY to paint the heraldry.You can either apply the sticker after you have applied the primer,or before that.I would do it before applying the primer,so that I cover later with paint any glue left from the sticker,or use(VERY carefuly!!!)a surgery sculpel to clean the metal surface(which could not be done if I had used primer
This is a so called substractive method.I prefer the additive method,which is more dangerous and needs more practice,but it gives a better result!
2-No guides used here!When you'll be ready to paint heraldry,you simply start with a basic drowing,painting the corpus and the left leg of the animal(you may have noticed that most animals-lions,griphons,horses,unicorns-come in the same pose in different heraldry...).No detail on your drowing yet.Continue adding the head and left members(without adding claws,tail,hair maybe or any hightlights).
I forgot to mention that all of these should be painted in your basic color mix you gonna use for the heraldry.
Now start adding the details.In this point you may make mistakes,so you may correct by lining with the color of the tunic.After you have succesfully added every detail,start highlighting your heraldry.
If on a shield,you could start making it dirty and scratched,using several well-known techniques.
I hope I helped!
Cheerz!
-Kostas.
