My set up is a MPLS/L3VPN core network and within my multiple VRF instances I have import and export policies where I add (export) and match (import) on community values. Therefore looking at the juniper technote example what exactley does auto-export feature do when I want to do route sharing between local VRF instances, when I am already adding/matching community values in the bgp.l3vpn table for remote routes and now wanting to do route sharing between local VRFs?
The standard VRF import and export policies affect remote PE prefix leaking. Meaning, import policy on a local PE tries to match the route-target applied via export policy on remote PE and if there is a match it installs that route in vpn.inet.0 table.
However, scope of auto-export is local. It doesn't affect the remote PE prefix learning. When you configure auto-export, the vrf-import and vrf-export policies are compared across all VRF instances on LOCAL PE. If there is a common route target community between the instances, the routes are shared.
Here is an excellent blog on auto-export:
Here is an example on practical use of auto-export:
PS: Please accept my response as solution if it answers your query, kudos are appreciated too!