Calligraphy pen in sanskrit and tibetan?

Unless you "grow up" learning to write in a Northern Indian alphabet, you will have some difficulty with the thick and thin lines. One solution is to use aleft handed fountain pen (if you are right handed). Tibetan is quite different from Devanagari. I have heard of Tibetan teachers in Nepal and India cutting the nib (point) from a cheap fountain pen. This simulates a bamboo or wood pen.