cross-process simply means using the 'wrong' chemistry process to develop the film you are using. example, slide film uses e-6 process, and color negs uses c-41. exchange the chemistry process around and you get unpredictable results and colors. (of course, after the cross-process, slides would become a color neg, and vice versa). there was a website which did an experiment on various cross-processes and you can use the results as a rough guide to the kind of effects you could achieve.
now..if only i can google it again..please be patient with me..
the important thing to take note about the Holga is..it has only 1 fixed aperture and 1 fixed shutter speed (namely f/11 and 1/100s). you have to work within this 'handicap' to achieve relatively 'proper' exposure (play around with film ISO speed, flash, ND filters etc).
usually the colors can be boosted/saturated in the computer. very rarely the colors that come out from the holga are exactly what you want. likewise for b/w.
