I recently watched a video by someone on GT6 ore generation, https://www.youtube.com/watch?v=OcfcHN5r0ZY. It’s 6 months old and about the distribution of ore (ie where it spawns) and doesn’t contain any specific techniques for finding ore as far as I know.
You could also go look on a wiki for GT6 (for example, https://ftb.fandom.com/wiki/GregTech_6/Stones_and_Minerals) about where ores spawn in relation to Y levels, stone types, installed mods and stuff like that.
I don’t really know how to find ores that well either, so I’d be interested what others say on this topic.