There is nothing more annoying that having to allow your local subsets across multiple windows boxes using the GUI, the margin for bordem related error is massive.
This simple script allows all the private subsets quickly.
new-netfirewallrule -RemoteAddress 192.168.0.0/16, 10.0.0.0/8, 172.16.0.0/12 -displayname "Allow Private subnets" -direction inbound -action allow