I've just seen this thread,or I would have replied sooner. I have a V35 with 40mm and also found it difficult to remove. It just needs some force whilst holding the lens mount still. The Ilford Multigrade paper includes a data sheet with filter values specifically for the colour head on this enlarger. This is what I use and it seems to work. There was a variable contrast module available, but they don't appear often(without the enlarger!) and when they do, they are expensive. I hope you enjoy using the V35. It is a superb enlarger.