Q: I keep trying to but it ends up sounding weird, in a way that other songs in 6/4 don't.
A: some songs are naturally gonna be in 6/4. so if you write 100 songs, i'm pretty sure some of them will end up in 6/4. for best results, i'd recommend don't predict which ones are gonna be in 6/4. but if you do 100 songs, i'm pretty sure you will get at least one that's in 6/4, and then you will finally be able to get that "i made a 6/4 song" badge for your coatsleeve that you've been craving