Well, emulating film-effects in camera rather than post-process has some advantages:
- you don't allow yourself to mend bad photos, especially when you shoot JPEGs, this is very similar to film because it makes you shoot more carefully
- less worry about post, just shoot and enjoy the moment, just like film
- concentrate on the subject, not how to make it looks better in post
- faster workflow
So, because film has better highlight detail than shadow (opposite in digital), you want to
switch on the highlight protection option, then
turn off the shadow detail option, both in the menu (or info button quick menu).
Then, increase the contrast until it resembles Tri-X or Ilford HP400 (both have higher contrast). Then shoot at ISO800 (Pentax's ISO400 is still too good damn low noise) or higher, until you find the balance ISO.
You may want to tweek sharpness (film is generally less sharp than digital) but that is for later. Concentrate on contrast and grain (noise) emulation first.
You also want to save the settings to one of your USER dial mode, so it's easier to switch from normal digital profile to your personal film profile. Good luck!