I integrated my site the other day. Here’s a few things that helped me when developing my bbPress theme.
1. Point its CSS to the corresponding WP themes CSS so that there’s a common stylesheet between them. For example: http://mysite.com/wp-content/themes/mytheme/style.css
2. Do the same thing with images. For example in your bbPress theme use http://mysite.com/wp-content/themes/mytheme/image/image.jpg
3. As mentioned above you will need to duplicate content from WP theme. I find that if I cram everything before the forum content into header.php and everything after into footer.php it clears up the rest of the bbPress templates for me to modify as I wish.
Hope this helps.
You can see what I did for my site here: http://tiptaptip.com and http://tiptaptip.com/forum
