Richard is absolutely right of course.
Flattening both sides is a machine approach.
  You can shim up / relieve the bottom easy enough.
There is no bonus at all for a finished bottom.

If you are doing it by hand let it look a little like it was done by hand.
There is no bonus in copying K-Mart with hand tools.

A Handyman #4 will do if you have to.
A more solid jack plane with a goodly camber on the razor sharp iron 
will hog more chips faster though.

Use your winding sticks to see where its the worst.
  Go diagonal or even straight across to start.

No time to squinge along and look at shavings etc. Dig in with a will 
and hog some thick chips fast!
When you get closer its time to slow down and use a longer plane.
   yours scott

-- 
*******************************
    Scott Grandstaff
    Box 409 Happy Camp, Ca  96039
    scottg@s...
    http://www.snowcrest.net/kitty/sgrandstaff/
    http://www.snowcrest.net/kitty/hpages/index.html