Hi Alex, I have tried a number of different methods to fill cracks/voids on my turned pieces over the years, including CA glue, PVA Glue, Milliput, epoxy resin resins etc, each with a measure of success. I have recently changed to simple wood filler, which I sometimes colour. The problem with 'pourable' resins is you are reliant on gravity doing its bit,however, like others have mentioned curvature of the 'piece' may require damming and or gentle heat to release air bubbles (Ok you could use a Pressure Pot to do the same thing).
With the wood filler method, I use Ronseal Hi-Perf Filler, you can work the paste into the voids, BUT you have to be quick as especially in summer it goes off quick, so little and often.