Cross VLAN ChromeCast Firewalling issues

Hello everyone.I have an interesting issue, which I believe is unique to me, or at least I can't find any information online about how to fix it.

I got a chromecast the other day, and since I have a slightly more complicated home network than most (VLANS) I went to put it on my IoT VLAN.

I then went to enable Mdns reflecting on my router (unifi) and hey presto, I could connect my PC to the chromecast across vlans.

I then went to start to lock down the firewalling for it to try achieve two thigns

1) I dont want all mdns queries going to all my vlans (EG I dont want my network printer being sent to my security vlan)

2) I want to control what VLANS certain devices can communicate with, (EG people on my guest network can see the chromecast so they can cast to it), but not see my printer for example

I set a few rules in place to try and restrict this down, and it worked, my laptop could not see the chromecast, but my desktop can (assuming established rules are allowing it though)

however I can't seem to find what ports need forwarding where to allow it though.

Everyone online is asking about cross vlans, but nothing about firewalling / restricting.

Does anyone have any insite on how I can setup my rules to achieve what I want

As a side note: People say online "Just make a new VLAN and put the chrome cast there"The problem is im out of SSID's on my wifi, and I dont really want a whole nother vlan for just 1 device.