Use Diamine Onyx black or Iroshizuku Take-Sumi. I feel the diamine is "wetter" than the Take-Sumi.
So it should be OK to leave them unused for 2 weeks or so?
The feed/nib takes bl***y ages to dry. I quite like my Sonnet for that, I can dismantle the pen and clean it separating the nib and feed, let it dry overnight-job done.The others, like my MB 146 and Pilot Sterling where I cannot take them apart take longer. I let them soak in water for an hour or so and stand them nib down on some folded up kitchen towel. Periodically puta few drops of water into the feed, repeat till there is no residual ink!.