As far as I know Tantric-Energetic practices are posterior to Tipitaka’s.
The subject is too vast, one could write here pages and pages.
So i’ll try to sum up as follows : you don’t need to directly focus on the chakras to activate / stimulate / open them, i.e. by improving your gati you’re working on the chakras mostly muladhara and swadisthana- which are fundamental to awake Kundalini.
Also anarya jhana by focusing on the air through nostrils can open sushumna.
There are so many techniques to work on the chakras, perhaps even too much… it’s partly a matter of pure creativity/ intuition.