Political Borders Needed!

[Nabi]

On the following map, I've created my first draft of the grand continents of Bsopura and Sumara, using a tutorial from this website. I'm fairly happy with how it turned out, though I think it could use some significant improvement: namely, in the creation of more accurate/realistic/good-looking political borders. To give a general sense of the history, the top-left country is an alpine empire, fairly militant and eager to take territory and "reculturize" it, renaming cities, and moving in huge amounts of immigrants. They are a Germanic country, if I were to transpose them into Earth. The top-left country, one with more of an Asiatic influence, is a quiet country of farmers and monks, a fantasy Nepal or Bhutan. Since the Germanic country lacks significant arable land, they depend on these fiercely nationalistic people for food, which keeps them relatively safe. In addition, their good relationship with the middle country, the local superpower provides quite a bit of backup. The middle country is like a mercantilistic Morrocco: trading tentacles everywhere, with a decent military, largely made up of mercenaries and highly trained knights and cavaliers. They are the primary trading partner of the bottom country, a nomadic people, roughly analogous to Old Testament/Torah era Hebrews.
Any and all help is appreciated!

Edit: Specifically what I'm looking for is DIY advice: though if anyone wants to use the existing file and add edits onto it, that'd be appreciated as well. Thanks so much.