Yes, that should work.So if I breed them to a mix (pea plus straight comb) with pea comb, I should get more pea comb and less straight comb and the percentage goes up when mixed pea comb chicks from this is line bred to pea comb down the line, until they only reproduce pea comb chicken?
You can probably save time by breeding from only the pure pea comb chicks in one of those generations.
The pea comb gene makes the comb & wattles much smaller when a chicken has two copies of the gene (pure for pea.) The pea-mix birds should have normal sized wattles, and their combs should also be larger than pure-pea birds. ("Normal size" wattles being what you would find in a chicken with a single comb, or any other comb type except pure-for-pea.)