Hi @RangerZ,
As you suggested here, I answer to your comment:
I am not clear on the static route's purpose or how to configure this
The static route is needed for the router to know where to find your gest subnet in your home 
let' say, as an example:
- 192.168.1.0/24 is your lan.
- 192.168.2.0/24 is your guest subnet.
- 192.168.1.253 is the lan adress of the dumb AP on your LAN.
- 192.168.1.254 is your router
Now imagine your guest connect its PC or phone with 192.168.2.10
when he goes on www.openwrt.org, the connexion will follow this way:
192.168.2.10 => 192.168.1.254 => the internet => www.openwrt.org server
ok now the data comes back from openwrt website to your guest machine:
www.openwrt.org => the internet => xx.xx.xx.xx (your public internet IP) => 192.168.1.254.....and....well your routeur will desperatly wonder where to find this 192.168.2.10 that is not a member of your LAN 
Static route is here for this: it has to be set in the router, not in the dumb AP.
the principe is just to say "if you look for 192.168.2.0/24, please forward to 192.168.1.253 (LAN IP of your dumb AP), because your dumb AP will know where to find 192.168.2.10
Then, how to set a static route may vary depending on your router, but you should easily find a static route section.
setting is not very difficult. basically, you have to set a target network (your guest subnet) and a gateway (here the gateway is the LAN address of the dumb AP).
There may be different way to proceed. Like I told on the other thread, I followed this howto
According to the website, this static route idea is a way to avoid double NAT, that could be an alternate way to proceed (I must admit I didn't checked all the other links).
Hope that helps