Only in a few cases of special symmetries, an analytic solution of Maxwell's Equations together with appropriate boundary conditions can be found. Among other things, difficulties occur because Maxwell's Equations represent a set of coupled partial differential equations (PDEs). Therefore, methods have been developed to convert the PDEs with boundary conditions into a set of ordinary DEs. This simplification usually goes along with a loss of accuracy. In this paper, the prerequisites for the derivation of (stochastic) Generalized Telegraphist's Equations (GTEs) for (irregular) deformed waveguides are discussed. It turns out that a systematic approximative derivation of GTEs is only possible in rare cases. In any case, further knowledge about the fabricational cause of the surface imperfections is needed to fix the stochastic properties of the GTEs. The method's application to an irregular deformed helix is used as an illustrating example.