Israr has provided incorrect information, shame on him.
In the model mode, changing the text font IN THE SKETCHER to filled does not work, as you figured out.
If the text is a sketched datum curve, you can add X-hatching. If the text is a projected datum curve, then you can not add X-hatching.
Since you want to then do a rendering, I would recommend you create the text as a solid feature. You can then change the color of the surfaces of the text if you like. Do a search to find instruction on how to create raised or indented text on a cylindrical surface.