Creating a new coupon type in code and adding fields

Problem/Motivation

I would like to add custom coupons that will give extra userpoints to users when added to a order.

Proposed resolution

Create a new coupon type in code with further filelds for the number of points the coupon gives, so far I have worked out that a coupon entity can be created using hook_commerce_coupon_type_info() but trying to add extra fields to this coupon type in the module initiation fails as the entity has not been created at this stage

Question

Are there any comprehensive guides how to do this? I also want to be able to add the points to the total and then apply after purchase.