Hi pmda - i think you are getting on the right track with this.
I think the key is to treat latin as a stand alone language, without reference to english (or whatever may be your native tongue). Words in any language are attributed to an image or concept in our minds, and this what you must refer to when translating.
In the case of 'duco', it is an image of something being in charge or control of something else, often combined with physical movement. 'To lead' can be a good english translation of this concept or image, but not necessarily so, because it has it's own image/concept connected in our minds which differs slightly.
It is important not to think of the english translation of the latin word, in order to then attribute the image/concept of the english word to the latin word. Although this may work initially, you will lose a lot of nuance and end up with seemingly non-sensical translations (e.g. i don't think i have ever said that someone 'leads' a pencil over a piece of paper, when I mean that he is drawing).
hope this makes sense...
“Cum ego verbo utar,” Humpty Dumpty dixit voce contempta, “indicat illud quod optem – nec plus nec minus.”
“Est tamen rogatio” dixit Alice, “an efficere verba tot res indicare possis.”
“Rogatio est, “Humpty Dumpty responsit, “quae fiat magister – id cunctum est.”