Community for small IX

Hello, We are running a small IX for around 20 members. A few months ago we moved on Bird and actually I am trying to add some standard communities to prepend or stop annoucing own prefixes to other members but can’t find examples on Bird docs nor by Google. All I found looks limited only to adding fixed community only. I think it is standard and may both work on filters for main table or via pipe import/export filters. But still – I can’t discover how to get and process (to block export) or announce (with prepend) received community. Could you please direct me (or send) some examples how to do this? Thank you, Peter