The key is to re-use the old C-clips from the axles you pull out. Do not use the new ones that come with the new axles. I had a Volkswagen tech help with the job and he said that the compression of the C-clip is what causes the majority of the resistance sliding the new axles in. In his experience new clips are more springy and cause significantly more resistance.

So put old C-clips on then use the axle itself as its own slidehammer to bang them in.