It's not too hard. Here's the way that I believe works best and what I did with invincible:
1) What we'd need to do is identify which content should be moved over. I think reviewing these on TopCow are the most important:
- Special:Mostpopularcategories and the top hits within them
2) Tag the pages you think are better on Top Cow with the category "Export Pages". Once you're done you export that category per the wiki instructions. I can do this too if you'd like.
3) Then we import that file here. There's probably some adjustments to the pages but once the content is here that's the easier part, just requires some elbow grease.
To close your wiki, you'd use Special:Contact and tell them to have the topcow domain redirect to imagecomics.