Probably the reason for the irregularity was the fact that you are supposed to keep swishing it around in the dyeing vessel and I obviously didn't do it often enough. The machine dye has the washing machine to keep everything moving so better success.
The packet one I bought does not need you to add salt but some of them do so please check. This varies between the Dylon ones also as one packet said add salt but the packet I picked up said 'improved' and you did not need it. The image above also varies slightly from my packet (I forgot to take photos)
It was £5.99 and has brought up the colour of the jacket by quite a few shades, a lot cheaper than buying a new jacket and as it was a favourite what would have been the point. I will definitely try some other colours now when I have something that needs a boost but I would stick to the machine option.
A couple of things to mention, there was a lot of dye collected in the rubber of the machine after I had finished. I had to give it a really good wipe out despite the fact that I had run a cycle to wash the jacket after the first dyeing wash. I then put in a full load of dark clothes to wash just to make sure I had got rid of any more residual dye.
There is also a limit to what you can dye with one packet and that will vary in your colour result also. Here I just did one jacket but it was quite heavy, a few t shirts, some underwear and a light dress could probably have been done with the same packet but again if you are changing the colour completely shades will vary.