Iodine isn't used for this anymore [much].  Iodine alone won't
permanently remove the image and it will come back in time.

You want something called "Farmer's Reducer".  It is a mixture of
Pot. Ferricyanide (pretty-much non-toxic, despite the name) and
Sod. Thiosulfate (photographic fixer).

A good camera store should have some packets of farmer's ~$3-$4.  The
alternative, and costing not much more than a few packets,
is to buy a jar of ferricyanide and a jug/box of fixer.  A teaspoon
of ferricyanide in a pint of fixer will permanently remove the
photographic image in a few minutes.  100g of ferricyanide (~$7)
and 16 oz of "rapid fixer" concentrate ~$4-$5 will make up 5
quarts of farmer's.  The jar of ferricyanide is enough for
~50-100 quarts, but it can be kept for years and years, you
will only have to buy new fixer.

If you can't find the stuff locally then try B&H photographic
in NY.  http://www.bhphotovideo.com/bnh/controller/home and
search for " farmer's ".

Farmer's only lasts 1/2 hour after it is mixed up, a problem
when buying the packets - but you don't have to mix up an
entire packet at one time: mix up part A and part B and
combine the two only when you are ready to use it.

You don't need to make up much - just enough to cover the photo.

India ink my have trouble sticking to modern photographic paper:
run a few tests first with ink on a photograph.

  Actually any reducer can be used. Iodine has the
advantage that the reduced area will not develop a yellow
stain over time. This happens sometimes when a Ferrocyanide
bleach is used.

 One form of Iodine reducer is"

Water                1.0 liter
Potassium Iodide    60.0 grams
Iodine crystals     20.0 grams

Make sure the Potassium iodide is completely dissolved
before adding the Iodine.
 This will leave a red stain. Clear it by treating in a 2%
solution of sodium bisulfite.
 Then fix in a _rapid_ fixer and wash.

 A ferricyanide bleach can be used. I would suggest one
using some posassium bromide such as the bleach for indirect
Sepia toner. The fix in any fixing bath to remove the
resulting silver bromide. A suitable bleach is:

Kodak T-10 Bleach

Potassium Ferricyanide            30.0 grams
Posassium Bromide                 15.0 grams
Water to make                      1.0 liter

 Treat the print in this until the image turns cream
colored all over. Then rinse for a few minutes and fix in a
normal fixing bath for 2 to 4 minutes. Then treat in a wash
aid and wash as usual.
 See if your library has a book called _Photographic
Amusments_. The original was by E.J. Wall and his name was
carried over on the numerous later editions. The book has
all sorts of tricks like this in it.
  Another method of turning a photo into a hand drawing
requires no processing at all but is tedious. Put a sheet of
drawing paper under the enlarger and project the desired
negative onto it. Use a large stop to get a bright image.
You must work in the dark. Using drawing pencils fill in the
bright areas of the projected image until it is uniformly
dark all over. When you look at this in the light you will
find you have drawn a positive image in pencil. With
practice you can learn to make either detailed or soft
drawings, and of course, you can retouch as desired in the
drawing process.