Easily reattach heat sinks during thermal paste reapplication?

Hi, I am using iFixit’s RROD kit to repair the thermal paste on my fat Xbox 360 and I’m stuck at the part where you reattach the heat sinks. I can’t seem to hold the heat sinks in place while I tighten the screws; the washers keep falling out. Any tips for how to actually screw the heat sinks back into place?