Open the can with a can-opener (manual, not automatic, if possible) and deploy the content all over the keyboard. Then scream CLEAN, CLEAN, CLEAN and you're done.
Ok, sorry, fun stops now. You shouldn't use a can of compressed air as it can condense in switches mecanism or just push the dirt between the keys into them, it is preferable to use a vacuum. If you want an extra clean keyboard, you should use a keycap puller to remove the keys properly and then use the vacuum again, and cotton swabs.
There's a gret guide here:
High quality mechanical keyboards can last for decades, and Das Keyboard products are no exception. There is one catch: dust and grime will overtake a keyboard long before its switches or electronics begin to fail. Cleaning, the most important keyboard maintenance task, will keep contaminants in...
www.daskeyboard.com