Jz bhai thanks alot for the appreciation.I am still a noob in this regard and under the guidance of Ustaad Jee vague_one. 
As for the engine bay, polishes attract alot of dust so avoid using them.Instead you can use a liquid solution from Turtle which is known as Turtle Pre-Soak Cleaner.You can easily find them from SACA Plus on Montogomery Road which is right next to Moeen Centre opposite to Shell Petrol Pump.
Now for the scratches, you mean the scratches caused by washing which are swirls.Right? For that you can use Meguiar's SwirlX but you will be needing a power tool like Rotary Buffer for that.If you are new in this regard, you need to practice the Rotary Buffer.Other solution to pull out swirls by hands is Meguiar's Ultimate Compound.Let me know if you want Meguiar's Ultimate Compound or SwirlX.I will refer you to a person
