Would suggest caution in using Engine Flush as it actually does flush out every loose particle in the engine/head. Use half a bottle only if u must (150ml max).
Ceratec is a great product, and I recommend it if u can afford it (minimum PKR 2600 for a bottle).
Use the Engine Flush as prescribed on its bottle, pour in the Ceratec, and add your choice of engine oil.
Do note that most quality oils will already have detergents and other 'cleaning' elements added during production, and will clean the engine as it works/lubricates.