Het Pied x Het Pied

Normal Pied
Normal Pied

--------------Normal-------------Pied
---------Normal--Pied-------Normal--Pied

So you will have:

Normal Normal
Normal Pied
Pied Normal
Pied Pied

So 1 in 4 are Pied, 2 in 4 are Het Pied, and 1 in 4 is Normal. Since we can not 100% know which are pied and which are Het Pied you subtract the Pieds from the mix, leaving you with 2 Het Pieds and a Normal. 2/3rds of the non-Pied offspring are Het (66%) and 1/3rd are Normals (33%)

Pied x Het Pied

Pied Pied
Normal Pied

--------------Pied----------------Pied
---------Normal--Pied-------Normal--Pied

This 2 in 4 are Pieds and 2 in 4 are Het Pieds. All offspring that are not Pieds are Het Pieds, thus 100% Hets.

I assume you already figured this out, however I thought I would lay it out easier for you, and in a method you can use yourself (and you can keep expanding as well to 3 or more tiers).