The good news is that both of these cameras do not need batteries. They are purely mechanical and are powered by winding up the lever on the side of it. Also, both of your cameras take regular 8mm film, not super 8. (Regular 8mm is sometimes referred to as "double 8mm" due to the fact that a reel of regular 8mm film comes from 16mm film that is modified so that it can be exposed a second time on the other side of the film.) It is better explained here http://www.filmtransfer.com/film-faqs
In terms of loading, Zac Fettig posted a good video but part 2 (watch it here: http://www.youtube.com/watch?v=SjMtkNaQ5kw ) of that video may be more informative to your camera type. I have a Keystone K-25 which loads similar to how the Brownie camera in "part 2" loads, and from the looks of it my K-25 is very similar to your K-26 and K-30.
Luckily you can still buy 8mm film, in color and in black in white. As Zac said you can buy it from Spectra, but also from http://www.zerelda.com/internationalfilm/internationalfilm.html If you live outside of the US there are also other sellers in various countries.
In terms of processing this website seems to be the cheapest http://www.dwaynesphoto.com/newsite2006/movies-ektachrome.html
Your ISO is definitely important to keep in mind when adjusting your f/stop. However it's my understanding that as long as you have the correct film gauge for your camera (aka 8mm, Super 8, 16mm, 35mm) you can use any ISO.
In terms of changing your shutter speed, if it's capable of changing shutter speed your camera will have some kind of notch to adjust it. My K-25 can't change shutter speed or frame rates, it doesn't even have a focus ring. If your cameras are like mine then I believe the only thing we can change is the f/stop. I've been digging around for information also and from what I can gather, old 8mm cameras usually have a shutter speed of 1/30 and a set frame rate of 16 fps, and newer models did 18 fps. However, that's generally speaking and it doesn't necessarily mean your cameras are like that.
Hope that helps. Good luck, dude!