Can I clean the pen?
The Bulkfiller mechanism allows for a great flow to be rapidly sucked into the pen and be pushed out again. This causes a lot of internal turbulence which thoroughly cleans the pen for an ink swap.
I noticed from some videos of the demonstrator where there are ink stains visible in the cap. Is this normal?
That is indeed a downside on a demonstrator. It requires regular cleaning. Many people desire a wet nib, which requires alteration of nib slit and feed. The feeder will therefore hold more ink. Drops breaking lose and collecting in the cap when handling or carrying the pen is unevitable. This also happens with dryer nib units and is considered normal. Much depends on how often the pen is used and handled.
Please check out the how to instructions page on the cleaning video.
Does the piston have to be lubricated?
For thorough maintenance, it is indeed advised to lubricate the piston every once in a while with silicone grease. An indicator on whether your pen needs to be greased is when you experience some resistance moving the piston.
A good regular alternative for silicon grease is to use Vaseline instead.