Decanting hair conditioner from one bottle to another. totally not putting the cheap stuff in the posh bottle to deceive dd 

Both bottles are very rigid - not very squeezable
Both have exactly the same size neck
The hair conditioner is VERY thick
I've had the two bottles balanced on end neck-to-neck for a whole day but the conditioner is so thick it's not dropping down into the posh bottle. If I try to squeeze the stuff in, (necks touching) it's so thick the air can't move upwards from the lower bottle and it farts out of the join sideways - over me! How can I fill up this bastarding posh bottle with the cheaper stuff without having to resort to physically cutting open the cheaper bottle & spooning the stuff in?
I'm looking upon this as an engineering problem, 