I used to do rinse out conditioner first, now I go straight to DC. That's only if I'm dcing on wet hair which I only do if I clarify and my hair is super stripped.
I usually DC on dry hair, wash/co-wash and then get out.
I Do Both. I will Co-Wash with either Millcreek Keratin (if I feel I need a boost of Protein), Something Super Moisturizing (if I feel my Hair needs an additional Shot of Moisture), J/A/S/O/N Biotin or Nutrine Garlic Conditioner (to counteract potential 'shedding').
The Co-Wash Conditioner I use for a 'special' purpose. i.e. protein, moisture or balance.
I condition first so that I can detangle under the running water (I'm a sink washer) and then if it's time to DC I'll do that. I only DC twice a month.
My DC goes on better after I my hair is wet so I co-wash first. My hair dresser says that the heat opens your cuticles and your pores preparing your hair for a DC she might be wrong but I still follow here directions because her hair is pretty and she does a good job. HTH