Rapport with manufacturers comes only from clothing sales. So, in order to increase rapport with them, you need to stock their items, and have customers buy them.
You have the right idea by placing their clothes with fixtures. Enhancing their level will also increase the appeal and demand of the clothing. But by enhancing all clothing, you're competing with yourself. Customers with a finite budget can only buy so much, so unless the clothing you have stocked has the highest appeal, chances are extremely good that they won't be buying much of it. That means the enhancement is essentially wasted money.
Tips for increasing rapport with a single manufacturer:
- This sounds like a no-brainer, but don't stock other manufacturer's clothes!
- Exception to this rule: Clothes that are compatible with the manufacturer's offerings. As long as they're on the same floor, you will gain the compatibility bonus.
- Caveat: You don't want to be selling much of this extra product; it's there only to boost the demand and appeal of the primary product. So don't place it in a favored location, like by the windows.
- Get a staff member with the highest level of Craftsmen you can to build the shelves. Simplest way to do this is to send all the rest of the staff on the floor to a different floor, and then place the item. The higher the staff member's Taste is, the better the demand. So a very high leveled Craftsman can provide the maximum bonus.
- If a shelf or rack has already been built, and the appeal and demand isn't high enough, remove it! You can rebuild it, following the tip above.
- Try to staff the floor with people that have the Bulk Shopper skill; that will increase the number of items bought.
- If the manufacturer focuses on only men's or women's clothing, try to give the staff on that floor the Men Magnet or Lady Magnet skill, too. That will draw more customers to the floor, leading to more sales of those products.
- Occasionally you will receive items that will increase demand on a single piece of clothing. This can be used as a boost to increase sales, but remember, the boost is permanent. If you later switch to focusing on another manufacturer and remove the original clothing, the item's been wasted. So be careful relying on them.