The fastest way to stain a fence is to have a group of people do it. I helped stain a fence this morning and we had four people. It took us four hours using paint brushes, sprayers, and rollers. I would get a sprayer that sprays an even coat.
grapevine
There is no fastest way, there is only the way. Wait. It is possible that you can speed up the process by exercising, but the increase is negligible.
I would need to know what you want to plan, to advise on the fastest way to do it.
Running.
The fastest way a gibbon can get through the jungle is by jumping from branch to branch or going from vine to vine.
Belt sander the fastest way.
Ask your neighbors if they care.
Use fantastic with bleech it works
Write a proper sentence so we can understand.
grapevine
The best stain to use on a wooden fence is the type that has a sealer mixed in with it. This will save you time and money because you can stain and seal all at the same time. The best stain to use on wood fences is a dark stain.
airplane is the fastest way!
There's no "fastest way"
You might be able to save a tired fence by treating with a good wood preserver/stain. Wood that is actually broken will need to be replaced with new pieces.
To get rid of sweat stains the best thing to do is use a good quality stain remover. It is the fastest way of removing these tough stains.
A barrier
If it is your fence you can injure yourself any way you like; if its not your fence then you'll have to get permission before you injure yourself.