Yes, you can use it dry. Not as effective since Bathmate devices are meant to use for wet purposes, creating the optimized compression and vacuum pressure.
DLD made this pumping routine:
Get a Bathmate Hydromax, Bathmate X-40 or Bathmate X-40 Realize Instant Usable Size! Perfect for Girth and Length Expansion! ORDER DIRECT FROM THE MANUFACTURER USING THIS LINK I thought I should make a post on this topic as I get many questions about the Bathmate and newbies wondering how to...
mattersofsize.com
It appears you're chasing after girth. There are many girth routines done by brothers here. Brother
@huge-girth can coach you on optimizing your girth for his service, or you can read up brother
@squirt_inducer_man PE journey, as he has one of the best documented progressive growth.