We carried around the large sums of cash........we used our credit cards (visa) when needed but check with your credit card companies as some charge overseas fees of up to 3% of the purchase price (can add up for hotel etc).
For small places, souveniers, etc, we paid in cash that we got converted to rubles at our hotel, no problems with that at all. We only carried in our 'wallets' a small amount of money and the rest DH wore around his waist and I around my ankle...........we were there in winter, and I wore my mid-calf high boots the whole time.......and loved my ankle money belt as I put it inside the cuff of my boot and NEVER worried about it at all (no one could steal, or detect it was there at all). This wouldnt' work in summer, but guess there has to be some benefit to being in Moscow for a month in the dead of winter!!
To be honest, we paid a large amount of our cash out pretty quickly when we got there, so it wasn't as bad as it seems!
We flew through Munich, Frankfurt and London on our various trips and can only say that the bummer was at Frankfurt all the smoking everywhere.......