Product Prices and Promos

Community,

I'm trying to set up sale prices in OFBiz, but they don't seem to be
applied when added to the cart.

I created an additional ProductPrice of type PROMO_PRICE, and the
calculateProductPrice service finds it with no problem, but the default
price is always used when I 'addItemToApprovedOrder'.

1. What is the relation between various product prices and product promos
(and rules)?

2. Am I supposed to set the promo price, and create a blanket price rule
that says for quantity over 0 (PPIP_PRODUCT_QUANT) apply the
'PROMO_PROD_PRICE' promo action? If so, what's the point of specifying a
ProductPrice?

3. What is the overridePrice parameter for the addItemToApprovedOrder
service? It's a string.. Is it supposed to be a "Y"/"N" thing, or a string
representation of a price?

4. What is the difference between the PROMO_PRICE and SPECIAL_PROMO_PRICE
ProductPrice types?

Thanks,

Justin