I don’t mind using multiple skeins of yarn for a project but I much rather prefer that I didn’t have to. The main reason is that I have always hated having to tie the two yarns together and then weaving in the ends. It just looks messy especially with the big knot in the middle of your work. Then I found this genius way of tying two yarns together. I have only had to use this when I was using the same colour yarn, but I am sure it would work just as well when using two different colour. Below you will find the link to a PDF of the instructions.
I hope this tutorial helps.
Happy Knitting,