Slow bead leak on freshly mounted tires

After the last shop scratched my wheels changing tires, I decided to buy the equipment and do my own changing and balancing going forward. I mounted a new set of Road Attack 4s yesterday, only now I seem to be slowly losing pressure through the bead on both tires. About 2 psi a day, it seems.

I wiped the inside of the wheels down with windex before mounting the new tires and used plenty of lube, both tire mounting grease and some additional windex when that wasn't enough. The bead was very hard to seat on the front wheel, took about 30 psi. And once it did finally pop into place, I noticed bubbles in the residual windex/tire mounting grease coming from between the tire and wheel in one area. I was hoping I had used too much lube and it would seal once it dried, but this morning both tires seem to have lost another 3 psi cold compared to yesterday.

Did I miss a step, is there such a thing as too much tire mounting grease? Is bead sealer usually necessary? Тhe wheel's bead surfaces weren't dirty or corroded to begin with. I didn't want to use aggressive solvents or scotchbrite on the inside of the wheels, since I didn't want to damage the paint. They seemed clean enough to me, but apparently something went wrong.

I plan to break the bead, re-clean the sealing surfaces of the wheels and re-seat the bead without mixing windex and grease this time. If anyone's got any other pointers on what I might have done wrong, please let me know.