Thing is, the Chakras are always open, they never close as such ... its a load of crap when you often read about exercises to close them, they close when your dead, and the physical is no longer required.
Its more a mental exercise to help the person doing said exercise to shut down or empower with seeing the chakras open or close, but trust me .... they are always open.
A simple effective method to help with Chakras, is to visualize yourself while in silent meditation either lay in, or having it poured through the crown, flowing into your entire body, the color Gold in a smooth gorgeous manner.
I'll have to get some exercises up on here soon
A good old book, no bullshit about astral travel which was written in the early 1900's but you can get reprints from the 80's and more recent from Amazon is those by Hereward Carrington and Sylvan Muldoon on the subject are very good, with detailed accounts, and explanations to it.