When you create a new profile field it will assign it a name i.e. field6. You can get this from the User Profile Field Manager after you have added it. In this example let's say the new field (field6) I added was the guitar they played.
You could add this to your postbit (or postbit_legacy) where ever it is you want your added field to appear.
Find:
<if condition="$post['age']"><div>$vbphrase[age]: $post[age]</div></if>
After add:
<if condition="$post['field6']"><div>Guitar played: $post[field6]</div></if>
It's all pretty well laid out in the postbit for you to follow along. Obviously it would be better if a phrase was added but you get the point. As far as doing it on a per forum basis, I am sure that could be added but would require more tweaking.