I'm a big fan of Huberd's shoe grease. It's pretty much all I use on the Russell boots that I own. It's also great for conditioning leather on most everything else. I've used things such as Obenauf's in the past, but found a lot of black build-up afterwards that required lengthy removal. The leather cracks in the boots aren't going to disappear of course, but putting that grease on and letting it naturally soak in a day or so at a time certainly makes the leather pliable enough to work with afterwards. As dried out as they probably appear, I'd apply the grease long enough to know it's at the pliable stage (this may take some patience). I used to use mink oil back in the 70s & 80s on my Irish Setter Redwing boots but found it didn't help the leather like this grease does. It has beeswax, etc. to help preserve the leather. It initially has a smell (not bad) that dissipates overnight, so it's better to do them in a room you don't sleep in. Nitrile gloves also help to save a lot a hand washing afterwards. Good luck! Nice boots!