Airbrush... actually I used Airbrushs before cameras, and you have to clean them after each colour, so I was afraid I would have to clean cameras after using colour film and decided to use b/w films.
Film speed depends on the metering you are using, for general stuff I used the Matrix and set the speed for HP5+ to 400, but for more critical work I used the spot metering connected to the focus field. Having a soft enlarger light I can develop films to higher contrast getting a bit more speed, getting closer to 400.

Regards,

Wolfram