I would start out using baby shampoo and see if this works. As long as it wasn't too drying to to his skin to where he starting scratching alot, I would just experiment with different shampoos. I used to bath my poodles once a week, but now if they don't get too dirty out in the yard, I've gone to bathing every other week. I hope this helps.
It might be the kind of shampoo you are using. I know with my own hair if I use a shampoo that is meant to moisturize it has a lot of wax in it and it takes one day before my hair is limp and oily. You might need a shampoo that really cleans his hair and then a light conditioner, nothing too heavy.
Right now we bath Olie every week with no problems BUT some dogs will get dry skin and irritated. I am still experimenting with shampoos with him to determine which is best. I had to do the same with my other 2 dogs. I wouldn't recommend conditioners if he's oily.....this will add to that oil IMO.
Well I can't recommend but people on here can and I started a thread in the grooming section where there are a lot of recommendations. I'd make sure to avoid anything that says "moisture" in the name of the shampoo and go with something that says that it rinses clean. If it's moisturizing it's going to have a lot of wax in it and then you will get build up and it will get oily.
Olie is still a pup so he has pretty soft curls now and we brush daily so no mats yet. He does get a little greasy/oily as well. I'm sure the thicker the hair and more they age conditioner will be no question.
Always make sure that his skin and coat isn't getting dried out. Some dogs need bathing more often than others because of the oils the coat produces, or if they play outside a lot and get dirty and stinky. You should be ok bathing more often as long as you make sure that he's not getting dried out and itchy.
You you insist on bathing him ever week then you will need to use the mildest shampoo possible or he will get itchy dry and irritated skin.
I would recommend a hypo allergenic/ tearless shampoo, most puppy shampoos are tearless and gentle. Wouldnt recommend a human shampoo (even a baby shampoo) as they are intended for humans and we have different ph levels in our skin, our shampoo can dry out a dogs skin.
Try to stretch it out to a bath twice a month if possible. Try using a soothing oatmeal shampoo also (maybe every other time).