For Cocker Spaniels I use a Slicker Brush and Greyhound comb like 'Vixen_with_velocity' said but I'd also recommend a rubber curry for bath time and a de-matting tool like the Matbreaker. Regular brushing should keep bad knots and matts out but I have a love affair with my Matbreaker and its always being used the two grooming salons I work at. Its a great back-up tool for those times where it brushing just gets away from you (it happens

) but I also find with my Golden Retriever that he sits in tree sap and it's impossible to get it out unless I bathe and shampoo him 6 times, this is where I use my Matbreaker. You should also have in your tool kit a nail clipper and if your planning to keep your Cocker longer, a Pin brush is great as it makes a good "in-between brushes" brush and wont break the hair shaft.