google analytics – Excluding Internal Traffic (Through Cookie on Another Domain)

Filtering Google Analytics internal traffic without IP or such: There are two domains I own. One that only internal traffic vists and one that should exclude internal traffic. I have installed a cookie that fires on the “internal domain” (through Google Tag Manager) but since that cookie doesn’t transfer over to another domain, I can’t use it to exclude users with the cookie on the other (main) domain.

Is there any good workaround where I can “flag” users visiting the one internal domain and then exclude them from tracking on the main domain?

So, the goal here is to filter out all internal traffic from the main domain by marking them when visiting the other domain (which only internal users can access).