I'm actually amazed that I managed to get 2 URs in 1 draw as well. The chances are like super low. Currently I have an idolized Umi UR, Kotori UR and 2 Nozomi URs so that would be 6 URs in total. Kinda regret idolizing my Umi though, could have improved my Cool team further by having 2 Umi URs instead.
Hmm, I don't know if it works for you guys but what I tend to do is keep spamming FP draws before a premium scout. If I fail to draw a single R within 3 scouts then I will perform my premium scout. I found out that I ALWAYS get a UR during my second premium draw through this method. Call it RNG or coincidence or just pure luck, but it worked out for me so yeah, just sharing this method with you guys. Try it at your own risk though