This space is intended to be more of a community as well, so please jump in and share tips!
I will be on a First Saver redemption ticket next week and I have a few sectors in Business due to it being a 2 class aircraft. Have you had any luck with accessing the First class section of the lounges before on the Business class sectors?
General rule for lounge access in this article.
But without knowing which airlines your are flying and what lounges you are trying to get into it’s hard to say for sure.