The quantities shown here make a concentrate:3 large crushed garlic cloves2 tablespoons paraffin oil1/2 litre water1 teaspoon liquid soap
When ready to use it, dilute 1:5 with water for general use and put into a spray bottle. (You may want to test varying the amount, dependent upon your target problem.)
Garlic is a very common and effective pest control agent as its properties are fungicidal, bacterial, nematicidal and repellent. Garlic is a broad spectrum pest control however so the spray is non-selective in what it kills - it will kill good insects as well as the bad. Avoid digging into the soil or drenching soil with the garden pest control spray as it will kill beneficial soil bacteria and insects.
Don't worry about peeling the garlic. Just separate the cloves and put them in your blender. When you strain the mixture, you will remove any bits that might clog your sprayer. See also Chilli Garden Pest Control Spray.