>>283037868
You basically can't train your chakra reserves. You get whatever you're born with. You can only practice chakra control to use techniques more efficiently with less chakra.
Kakashi can't do clone training like Naruto because it would burn through his chakra too fast to be of any value. This is true of most ninja.
Think of it this way:
Kakashi can focus on training for a couple hours, exhaust his chakra supply, and be unable to train any more.
But Naruto is a chakra monster who can train all day, run out of time, and go to bed with 90% of his chakra still remaining. He's not limited by chakra, he's limited by time. That's why clone training works for him.