to paint (someone) a picture：意思是解释某种情况,使人更加明白.
(to explain the situation; to make things more clear);
例如：In order for you to understand better,I will paint you a picture.(为了使你更能明白,我愿加以解释.)
He will try to paint us a picture when he gives a speech.（他演讲时,尽量想法使我们明白.)
When I write an article for a newspaper,I will paint my readers a clear picture.（当我为报纸写文章时,我尽量让我的读者充分了解.)
但是 to paint a picture,意思又有不同了.
例如：The artist will paint a picture of me.（画家为我画像.)
The artist painted a picture for his interior decoration.（画家为了他的室内布置而画了一幅画.）