This is one of my most used features in Launch Bar.

1. Select the text you want to convery and copy it.

2.  Activate and type 'convert', select the conversion you want

1. Paste the text

1. press enter, then copy the text

1. Go to where you need to the text and paste it.

Addendum:

The people at ObDev sent me some tips over twitter to make this even faster.