I always had a lot of problem to have a clean sensor. Everytime I cleaned it I get rid of the old dust and dry stains, but also got a lot of new ones. I feel one of the big problems was that the spatula I used didn't catch up the dust, more move it around on the sensor and placed it along the edges. Later I found after a tip from my friend spatulas with a top of micro fiber fabric. Now I have a much better result, but they are expensive, some take 7 Euro each for them, but I found a set with spatulas for 1 Euro each.
Some photos and text explaining what I do:
http://www.astrofriend.eu/astronomy/...ng-sensor.html
A big warning, it's very easy to destroy the camera, especially the shutter is very sensitive. I recommend you to not do this, leave it to a specialist. This is just information how I do it !
/Lars