Hello, i'm in trouble trying to make some shades surrounding my country borders. It should look like this:

erferfer.png
wedwe.png

I'm doing in Inkscape, so there's a tool inset, that makes indent and saves the shape. But the indent is fixed and there is a blank space between to borders then. So i tried to use dynamic offset, but along my shape there appears white spaces, like shape is breaking. Another method i used is to create thick 30% transparent line under original one, but it's impossible to paint one line in two different colors.

My question is: how people make these nice borders?

Original pics:
https://fennomanic.deviantart.com/art/Tiberic-Republic-733227066
https://nanwe01.deviantart.com/art/MotM-1-The-Italian-Campaign-of-1853-54-384918171