There are three different methods to save time and speed up your Western blot protocol: 

Use directly conjugated primary antibodies. For proteins of moderate and high expression, detection using primary antibodies conjugated to enzymes (ALP, HRP) or fluorophores will work well. Agrisera's collection of directly conjugated primary antibodies can be found here

Incubate several primary antibodies at the same time. Using this method, the detected proteins need to be at least >20 kDa apart from each other, and the primary antibodies have to have a known optimal dilution. Check out an application example here

Blocking reagent, primary and secondary antibodies incubated at the same time. This method shortens the Western blot protocol considerably. Use Agrisera's Incublocker, and store the primary antibodies in the Incublocker solution for subsequent experiments. Check out examples here
These methods are to be applied to already validated and well-characterized antibodies. 
  Save time and shorten Western blot protocol
 Technical blog