LC have a "LC Flush Procedure" on their website. The procedure is sort of buried in a report there that was done by Mola. Read through it and you'll find it.
I'm not so sure that the 15 or 20 minute flush they outline really does all that much. I've experimented (cautiously) with higher concentrations and longer exposure times. I've never pulled valve covers for a before and after look so I can't tell how effective the procedure is.