A few weeks ago I had a lot of trouble assembling 4" aluminum dryer vent sections. Not anymore.
A metal vase is shown with a 4" diameter dryer vent section. It (or something similar) does a good job of preparing the pipe ends for assembly.
Just press with some force the female end over the vase and the male end into the vase. It rounds things nicely and removes some of the imperfections that interfere with assembly of the pipe sections. It slightly flares the female end and tapers the male end (slightly) inward. It makes a huge difference in assembly.