Solo 401k to Roth Ira conversion latter

[suddenwealth]

I have currently been pounding my money into my solo 401k every year.  Once I retire, how do I go about slowly converting this into my roth IRA, so that I pay no taxes or penalty fees on it?  Am I simply able to transfer a small amount from the Solo 401k into the Roth IRA every year?  Vanguard doesn't allow me to do this, when I try fooling around with it online. Or, do I have to make a solo 401k to trad-ira transfer, then roll it over into the Roth IRA?  From everything I've read about the conversion latter online, there hasn't been any talk about the solo 401k to roth IRA, just the traditional IRA and 401k. Is there any difference? Also what is the maximum amount I could transfer this year that would keep me in the 0% tax bracket, assuming I had no other incoming?

Thanks for the help.

[forummm]

http://forum.mrmoneymustache.com/investor-alley/how-to-withdraw-funds-from-your-ira-and-401k-without-penalty-before-age-59-5/

You need to roll your solo 401k into a TIRA. Then you do the TIRA to Roth conversions. You may have to pay some tax on it depending on how much you convert and the amount of other taxable income you have at the time. You'll have to do your own calculations using a 1040 or 1040 EZ to determine what the max amount you could transfer without tax would be, given your personal scenario.