Normal shampoo or 2% Ketoconazole first?

Hi all. I have seb derm on my scalp. I’ve heard two methods to using 2% Ketoconazole:

1.) Shampoo with your normal shampoo (I use Pantene pro-V) to get rid of grime and dirt then use 2% Ketoconazole

OR

2.) 2% Ketoconazole first then normal shampoo

Which method do you do? I always thought the first method was the correct way but a derm I saw recently told me to switch to #2.