Block guest users from OpenWrt router/samba server

I hope this will be easy for someone to help me with. I have a router in a normal configuration connected to conventional ISP. On this router is a samba server add-on running with non-protected data but I don't want my guests getting into the data. I am going to add a secondary router, for my guests to get Internet access that has the secondary guest router WAN jack plugged into the LAN jack of my main router. Is there a line command to block guests that have wifi password for router 2 from accessing the server on So the gateway for secondary router will be the primary router Can I add a firewall command on block everyone on the secondary router frrom accessing the samba server on without also blocking the gateway part of the router/server combo, or do I have to now configure all my appliances that access the samba server with log-in credentials for the share? (I don't want the passwords really for the primary network wireless, only for the guest wireless.) Thanks!

you should probably set a static IP for the WAN port MAC address, of the guest router,
then create a rule that will block traffic to the lan zone from that IP.