I know this thread is a little old now but I wanted to share my experience of cleaning these out as per the video links.
I did this with one of the clearomisers that I have - took out the bung, rinsed it out with water etc etc, did the dry burn and left the unit to air dry (left mine for 24hrs). Reassembled, put new juice in, attached it to my battery, switched it on and......nothing. Then I found that if I took the rubber bung out it worked fine and had a fantastic draw/taste without that rubber bung thing in it
lol. Only problem is can't use this one out and about due to leakage issues!
So now on to the other one that I cleaned out using a different method - after taking out the drip tip I held it under a gentle running tap till nearly full, hold between fingers to close, shake it about, empty water out from the top - repeat as necessary to get rid of any old juice (smell etc). Then to dry it off I held it underneath my hair drier on the lowest setting. After all this, refilled (with a different flavour to the last juice used), fired up and worked perfectly - there was no trace of any mixing of flavours etc. So have found that there isn't any need to faff about too much with these things.
In fact, in my so far limited experience the less faffing the better
Hope this helps others out with cleaning these