Can you use some thermal paste instead of the thermal pads?

Yes, Thermal paste can be used instead of thermal pads. While thermal pads are less messy that the thermal paste, the result of using the pads or the paste are the same - they both conduct heat which assists the heatsink to dissipate heat generated by the processors. The advantages of the thermal pads over the thermal paste is that the pad can be placed with much more ease, accuracy and you do not have to worry about the thickness of the layer. Some would have the opinion that the paste is more conductive but other would argue that the paste will eventually dry out and it conductive properties are lessened. I hope that this helps...

Mark from iqFix.ie