The end cuts can be painted with anything which will slow the loss of moisture. Use whatever you have on hand such as glue or paint. Curing a stump is all about controlling it’s release of moisture.
Keep it horizontal for 5 years, elevate it for air circulation and periodically rotate it. This prevents the internal moisture from settling. Keep it in a place that provides protection from outside moisture, such as a garage or shed.
Impatience to use the stump will result in it releasing moisture and creating mold in the workshop. I experienced all the mistakes due to my impatience.
I used stumps cured for one year, two years, and 3 years, while patiently waiting 5 years to cure some properly. There is a big difference between them. It was worth waiting 5 years. The stumps that cured 5 years have not created any moisture or mold trouble in the workshop and seem to be tougher.
Therefore, in my experience, nothing can shorten the 5 year curing period and nothing can stop the release of moisture, not sealing the ends nor periodically turning it end over end when it is standing in the workshop.
I think most stumps develop cracks, but proper curing seems to reduce further deterioration.