Most dogs are going to shed, but at times it's worse than others. There are all kinds of different factors that might be at work. What did you use for shampoo? Did you use any type of conditioner afterwards? Did you use a hairdryer? What's your weather like?
You'll probably need to get some type of long bristled brush (maybe even just a vent brush, just make sure it's got rounded tips so it doesn't scratch him) and spend some extra time brushing him outside. The birds will LOVE it since nesting season is coming up soon. Dog hair makes wonderful, soft lining for nests, and Spaniel hair is so soft.
At a year old, he may be getting rid of the last of his baby coat, too. If he continues to shed excessively, it might be a good idea to get him a good vitamin/mineral supplement specifically to enhance his coat.
Bathing may have worsened the problem temporarily by drying his skin somewhat. A good conditioner will help, and again, a supplement will help.
Perhaps most importantly, examine his diet. Really look at what's in his dog food; that can make more difference than anything. Since I convinced Charlie to switch to the Innova, Bimmer's shedding has been almost non-existent, which is amazing considering the density of his coat, and Shiva's coat is soft like velveteen with very minimal shedding. I'll give you the link to the NaturaPet website, where you can use the comparison utility to look at what's in different dog foods. It's really a helpful site.