looking for some help with bgp extended communities

Hi networkers, I'd like to use bgp extended communities instead of communities for my routing policy so that I can use the 4-octet ASN. However, I am a bit confused by the route target vs route origin (and not having other kinds). Would it be appropriate to use the route origin (as opposed to the route target) kind of ECs to hold the community data that I will use for routing policies? Or maybe is there a way to use the generic 0x04 sub type instead of ro and rt kinds? Also, is it legitimate to use some private ASN for global communities that can be set by any of my routers when talking to one another? Thanks, wt