Its not as simple as you think!
You need to have an understanding of genetics. Just as a basic guide line, I will refer to the Basics of Biology.
You have 3 possible outcomes. Take the famous flower colouring as an example.
If you have a red flower and a white flower[/color] and you cross-bred them.
You have three possible outcomes.
1) Red off springs
2) White off springs
3) Pink off springs
Obviously in the first two outcomes, one of the plants is known as the dormant plant, transmitting all its genetic code to the other plant.
What you want is the third outcome, where both genes have been mixed. However, the degree could also vary, Dark Pink, Light Pink, depending on how much genetic makeup has been taken from each of the plants.
Another challenge you will face is being able to determine a successful cross-breed, with the flowers its easy as identifying the colour code, with a cannabis plant you really need to know your two different strains and determine the outcome from your experience, or invest in $1000 of dollars to purchase your own lab equipments.
The mixing of genes depends on many factors, but in the end of the day, it depends mostly on the unique genes codding of each seed or plant.
From the batch of seeds you create, mostly they will have one make up, but some differences can appear, so from 100 seeds, you may get 5 red 5 pink and 90 white.
The first cross you make will be referred as F1, second cross F2, third cross F3 and so on.
The only way to perfect it is through experimentation and it wont take anywhere less than 5 Years for you to just be able to get the grasps of it, unless you have expert advise from someone who is experienced and can tell you all the info you need to know.
So it IS NOT SIMPLE and yes, for a newbie to believe they can successfully cross pollinate two strains and create their own strain which can hold up from the first try is far fetched.