A couple more tips:
If you can get away with using art that has the effect applied to it before you import it into Construct, then do it. For example, if you have a background image that is always blurry, then blur it in Photoshop before you import it. There is no sense in using a blur shader for that.
Of course, if you want to be able to turn the blur on and off at runtime for whatever reason then there's no getting around it, but generally speaking if the effect you need is always on, try to find a way to create it with assets rather than shaders.
Also, keep your shader use to a minimum. A lot of people go overboard with shaders when they first start using them, and for the most part they're not really necessary. Shaders are like strong spices... a little dash here or there can make a big difference in how your game looks. But use them sparingly or you will have a huge mess on your hands.