wondering if there is anyone out there who may be able to help.

I've recently moved from a Edgerouter lite to a Grandstream GWN7502. 

The experience has been very easy and for the most part much more intuitive than the Edgerouter. 

My basic network is a main LAN for the people who live in the house (192.168.1.X) on VLAN1 and a Guest network (172.16.1.X) on VLAN 1999. I've isolated the networks so both have access to the WAN but not each other. 

I have a printer at 192.168.1.106 which I would like the Guests to be able to use. I had this working fine on the Edgerouter but having trouble on the Grandstream which highlights my lack of networking knowledge. I may have fluked getting it working on the Edgrerouter ;-)

I can set a forwarding rule so that traffic from 172.16.1.X can access 192.168.1.106, which has allowed me to set up a printer on a windows computer through entering the IP address manually. But what i would like to do ideally is have the printer auto-discovered (eg AirPrint from ios). Under the current set-up that doesn't work. I assume to do this i need the printer to be exposed to the 172.16.1.X network generally but I'm not sure how to do this or whether there is a different way through static routing. 

Any tips or guidance would be greatly appreciated. 

Thanks in advance.