Dumb dog, smart dog...dealing with frustration

I'm having a difficult time dealing with my frustration with training more than anything. I have two dogs. One is a 1.5 yr old cocker spaniel. He's a very sharp dog, eager to please, motivated by food and affection and learns very quickly. I can usually teach him a simple trick in just 5-6 repetitions and can get it down very solid in just a session or two. He's fun to train because he learns so quickly. My other dog is a 10 year old basset hound. I swear he's as dumb as a box of rocks. He's motivated only by food and even then, he's very easily distracted. I can be holding a hot dog and he's distracted and wondering what's on my counters or what's in the trash or what's behind the refrigerator or whatever. I'm still working on getting him to sit on a regular basis. He will sometimes do it on command to get something from me but other times he looks at me like he has no idea what is expected of him. Getting him to sit and getting him to sit calmly are a completely different thing. The latter seems to rarely happen. At one point I thought I had trained him to not jump on the counters. He never did this when I was around at least. Now he doesn't seem to care and seems to have forgotten all the training.

How do you deal with frustration in training two dogs with such different learning speeds and capacities? I'm afraid I'm getting really frustrated with the hound and it's not helping the training process.