Renewed interest in 'line and wash' brought to mind a TV programme made some years ago. It was called 'Making their Mark' and was broadcast on the the BBC's 'Learning Zone.' It recorded four artists demonstrating and talking about drawing. One was Sir Hugh Casson who was videoed sitting on a folding chair drawing a little Baroque church in the parkland of a country house – he described it as a delightful 'rich man's God box.' His kit merely consisted of a shetchbook and a Rotring Art Pen. He incorporated a wash into his line drawing simply by spitting on his finger and smudging. Later on in the programme he refined his technique by wetting his finger with water from a plastic cup. I adopted the method the following day!
I've never enjoyed humping cumersome painting gear around and for years I used a cartridge sketchbook and charcoal. With charcoal you have to work at A3 or larger which makes you rather conspicuous, and it is messy. I changed to a portrait format A4 sketchbook which gives an A3 double spread if you need it. Looking back through my sketchbooks around 75% of my drawings use pen linework and monochrome or sometimes coloured wash.
The only drawback with Rotring Art Pens is that the ink is watersoluble which makes a fully developed wash technique difficult. It is possible to use waterproof drafting pens of course but the Pentel Brush Pen makes varied marks resultinh in more lively drawings.