thanks for your kind remarks.
The use of BGP communities is technically possible when you advertise multiple routes to each ISP.
You should use a route-map to set specific BGP communities on specific routes.
The route map can then be applied outbound towards ISP eBGP neighbor.
inside the route map the set command to be used is:
set community 12:34 ?
<1-4294967295> community number
aa:nn community number in aa:nn format
additive Add to the existing community
internet Internet (well-known community)
local-AS Do not send outside local AS (well-known community)
no-advertise Do not advertise to any peer (well-known community)
no-export Do not export to next AS (well-known community)
important additive keyword because actually multiple BGP communities can be associated to a BGP prefix (instead only a single route tag can be associated to an IGP route)
the neigh ... send-community is needed on both sides
What is most important ISP has to agree on using BGP communities and what BGP communiities values to use.
An handy command when working with BGP community is
ip bgp community new-format
that allows to see BGP communities as ASN:value in router show commands
in your case you can use two different BGP communities one for /24 prefix and one for /23 prefix.
the ISP knowing this can perform some actions based on agreed BGP community values.
It can be of limited use in your case.
Hope to help