In one of Paul Budzik's great videos he mentioned using dental 'paper points' to clean your nozzles and I thought I'd give them a go.
Like most medical supplies they're cheap (IMHO). I bought mine here for just over £4 and for that you get a nice plastic box with 6 smaller boxes of 34 points (why 34??) that will also set off your 'Ooh, those'll come in handy' modeller's gene:
Paper points by Ced Bufton, on Flickr
Paul kindly replied to my PM and suggested size 30 for my 0.2mm nozzle and size 60 for 0.4mm. I've tried them today and, as you can see on the lower one (small black blob), they certainly clear out the gunk that other things can't reach.
Note that if you soak the point in cleaner they're useless - they're designed to soak up... well, you probably don't want to know... so put some cleaner in the nozzle and use the point dry just twisting it a bit as you go.
Recommended!