I have used three popular E6 kits in the past, from Patterson Kodak and Jobo.
Although the mixing of the solutions do vary with the different brands, in proportions and time, provided the instruction are followed there will be no problem.
With the JOBO Expert System Processor, there is constant agitation, but I have not
had any noticable variation in quality when using hand tank processing - with inverting and rolling slowly during all of the first development.
As stated, the time and temp. is very important and has to be spot on for the first development, whether processing by hand or machine.
It is not at all complicated and well worth developing your very own method of working whether by kit or otherwise.