Cokin Z-PRO Filters or Variable Neutral Density filter

[enny]

Hi guys i have bausch and lomb anamorphic lens this is big i also have cokin z pro series filters that i have made attachment in front of my lens to use the filters it can be a bit time consuming using them my question is placing a smaller filter between taking lens and anamorphic lens any problems there or filters should always be at front of the main lens. And can you recommended a filter and would you use Graduated ND Filter  for video

 

Thanks for your help