that article was very good for telling yaZ how to use the eraser. it's a simple but effective tool.
another method is to use any of the lasso or select tools (freehand is probably best) if you want to work quicker at blending larger areas...and still retain a pattern or shape, like a jagged edge or isolated spots of one image or whatever.
like in that article, just get one of yer images and paste it over the other in a seperate document as another layer.......then use yer lasso tools to select the areas you want to erase from the top image. (use shift and alt. keys to add/subtract with the lasso tool for more accurate and easier selection) once you've selected what you want rid of, go to modify in the upper menus and go to FEATHER. (i think the feather range is available right there on the bar in 7.0 if you're using lasso tools, i may be wrong) this is the beut that automatically fades-out the distance from the center of yer lasso line. it softens edges and stuff. set it to whatever you want, like, um, i dunno, 50 or something, then just hit CTRL+Z to erase those selected areas. it'll reveal the image below and fade the cutting line to whatever feather amount you selected, giving an instant blending effect. take the actions back and experiment with different feather values if you're not happy.
it lets you make all sorts of wacky shapes if that's what floats yer boat.
[edit] by ctrl z i actually mean X. oops =/