In DCS World, air-to-air TACAN is commonly used for rejoining with an AI tanker aircraft, but here is how to use the system to locate other human-piloted A-10C aircraft. Special thanks to Wrecking Crew and Localmax for helping me research this article.
You can use the TACAN to find other aircraft, too. This could help us to help rejoin formations after a fight.
The short explanation is that the leader chooses a Frequency and the Wingmen use the Number of the Leader +63 (on the same X or Y frequency). Example: Leader is on 5 Y, so the Wingmen would be on 68 Y. Wingmen would now see the Leader on the HSI and the TACAN. In T/R mode you can also see the distance to the Leader so it can help to maintain a good Battle Spread.
When getting near the AO, TACAN should be switched off, because you transmit your position to the enemy, too.