Paint one cylinder with some high temp black, or powder coating. Put them in the oven at 350. Remove them from the oven and see which cools faster. It will be the black one.
Eloss=Econvection + Eradiation + Econduction
In a water cooled device, the largest loss of energy or heat, by far, is from convection. The Econvection would be the same between a painted and non-painted cylinder. The Econduction is also identical between painted and non-painted cylinders. This leaves Eradiation. The color black yields the highest Eradiation value, while a shiny mirror finish yields the lowest. Blue, Red, etc fall in between. So, according to the formula and 2 phd physicists in my office, the largest loss of energy or heat would be from painting your cylinders black.
Polishing your cylinders is probably the worst thing you could do if you were worried about keeping heat in your cylinders. But even then, it shouldn't matter, because the fact that the cylinders are water cooled, means that the largest loss of energy or heat is controlled by the temp of the water.