I'm going to dissemble my acer nitro 5 8300h 1050ti laptop to clean the cpu and gpu thermal paste . Can I use paper towels dipped in Mountain Falls 99% Isopropyl Alcohol First Aid Antiseptic for Technical Use? Also can I clean the outside of the contact surfaces with isopropyl alcohol ? Can I use q tip to clean thermal paste dipped in isopropyl alcohol and dry the contact surfaces and around it dry with q tip or wait for the isopropyl alcohol to dry by itself?
99% isopropyl alcohol with a cotton swab is excellent for the task. Clean all the old paste from every surface, including the extra that wasn't in contact with the heatsink. You don't need to dry it off, as 99% alcohol will quickly evaporate all by itself, leaving the surface shiny clean. If it doesn't, you used too much.
Use only high quality thermal compound.
Don't be cheap. You want it to perform at peak efficiency for years to come. Good quality compound isn't white or thick, and doesn't dry out quickly—unlike the crummy paste you probably just removed. The good stuff is noticeably thinner in consistency than toothpaste.
If the surface is small square, apply a dot in the middle and let it work its way out under the pressure of the heatsink. If it's rectangular, apply a bead in the middle along its length. You don't need much if you bought good quality thermal compound. But if you bought thicker cheap paste, you have my condolences.