Amazon.com: Arctic Silver 5 AS5-3.5G Thermal Paste: … I very thoroughly clean the CPU of any year-old thermal paste with coffee filters/Q-tips and 91% isopropyl alcohol, re-seat and apply the small pea-sized bit of paste to the CPU. … (eg isopropyl alcohol available at chemist shop) & swab, clean out old paste. Be careful.
https://www.amazon.com/Arctic-Silver-AS5-3-5G-Thermal-Paste/dp/B0087X728K