Spelling is a fundamental part of any writing. It allows a person to know anything at any point in time faster than any other thing dealing with writing alone.
It is the best time saver of anything dealing with writing.
Spelling can decrease the amount of time someone can relay information exponentially. Not just on the part of the person writing, but also on the part of the person reading.
For example, it is very easy to make sure everything is spelled correctly by using a computer. This is the simplest way.
Just typing something into google is very fast and it checks spelling.
In general, the better the word processor, the better your spelling will be.
For instance, Open Office is free and very good for spell check purposes. Microsoft office is another choice that allows easy access to a spellcheck. It doesn't matter how long you're writing, you will spell better and with less difficulty using a word processor.
A free one is available here.