Construction of multiple model forms and controllers

I have a problem with the construction of a sequence of input forms.
The model being created and edited is called a Portfolio. The
portfolio contains multiple subordinate objects, such as Stock,
AssetClasses, Sectors, and worker objects link StockPosition,
SectorPosition, and AssetClassPosition. I have the belongs_to and
has_many relationships working and have written scripts which
demonstrate that once constructed, the associations work.

My customer wants the Portfolio object to be created across 3 distinct
pages, call them P1, P2, and P3. I cannot seem to set up a controller
and action methods which will allow me to create the Portfolio base
object in a new/create pair of actions, and then allow multiple edits
on the object, call them P1_edit/P1_update, P2_edit/P2_update,
P3_edit, P3_update. I am also lost on how the routes should be
configured to do this sort of thing.

Most things I have done with Rails up to this point were based on the
RESTful style, which only allows for a single edit/update action pair
on any given object. So, how does one construct a controller/routes/
views set that will support a sequential creation and configuration of
a given object?

I have been at this for 3 days now and my hair is getting whiter. I
would appreciate some sound advice.

Thanks in advance for your help.