Using sensor swabs is the best accepted way to clean a sensor. Nikon only puts that warning in the manual to disclaim liability if you smash your sensor. The same technique that you used before should work fine now. You will, however, need the $80 AC power adapeter, or the camera will not let you lock up the mirror and shutter.
There is risk with this method, but the mirror will stay up on manual, "bulb" and the shutter release held down (I use my thumb). Some will feel uncomfortable with this though will work and continues to work for me. I use the Copper Hill stuff. I just couldn't justify the cost of the AC power adaptor for this purpose alone (for my use of the camera). I consider this a "safe" way to do the deed, others will not.
Instead of holding the shutter open using your thumb, why not use the "lock" on your cable release to do the job. Far more reliable than holding the shutter release with your thumb, assuming that you have the cable release cord.
There seem to be two minds when it comes to sensor cleaning. One group swears by swabs, the other (among which I am a member) believes in avoiding touching the sensor if at all possible. I have owned 5 Nikon DSLRs, have had to clean the sensors dozens of times, and have never resorted to touching the sensor. A gentle blow with a bulb blower while holding the camera upside down with the mirror locked up will nearly always clean your sensor. It will certainly handle dust. If you somehow manage to smear something on your sensor then I imagine you would need to use a sensor.
Don't use pressurized air (from a can), as it can damage things.
The way I approach dust on my sensor is three-fold:
1) Use a large blower bulb (I use Giottos Rocket Blower) 2) If bulb doesn't dislodge the dust, I use the CopperHill brush 3) If that doesn't work, I use the pec-pad/eclipse method
You also must consider your "dust tolerance". I describe my dust tolerance as "f/11 dust". If I can see it at f/11 (or wider), then I'll clean the sensor. I don't worry about dust at f/22 or f/16 unless I'm heading off to do major landscape work.
It is hard to keep ALL the dust off the sensor, but this works for me.
============================================== Darrell Young (DigitalDarrell) www.pictureandpen.com "Better too many words than not enough understanding." ==============================================