thinking using group poster to promote in active facebook group from other country
Are you using any software for automating your actions or?
If you are using Jarvee you can check this thread out:
Jarvee will definitely help you in this a lot. With Finder and Joiner tool you will be able to join many groups from the desired niche. You can search based on keywords and there are some filters available as well.
You need use Old FBacc search