Is this an overwintered hive? I assume you don't have any drawn frames for your super.
If the bees are busy and you are on a flow, they will draw out the comb fairly quickly in the first super. Some sugar water sprayed on the comb will probably get them up there to check it out, but I'd not spray it unless they don't start to work.
The second super of foundation is more likely to give you trouble, as they won't be in the middle of a big flow when it's time to add more space for them, and they will be less interested in drawing it out. What I would do then is put the new super under the first one, above the brood nest, and take a frame or two of capped honey from the first super and put them in the new box with a frame of foundation between them. This will get the bees working the new box, and they will draw out the frames of foundation in the top box if you still have a decent flow.
If you can find a frame or two of drawn comb to put in that first super it will speed things up greatly.
Peter
