I think I understand what you are looking for. Please all the God’s Daz sorts out the forum so that we can illustrate our explanations with screen shots once again.
If I understand correctly, you gave two examples the first a circle to which unless I miss read you seemed to imply that you have been attempting to add additional vert’s one by one to improve it’s visual appearance. If I’m correct; wrong, wrong, wrong.
Select the type of line circle to suite your needs and release your mouse button, do NOT double click your mouse button, nor should you validate or press the enter key. Instead look in the right hand properties window for the circle and near the foot of the top panel you will find a small box labelled number of points. Using either the up or down arrows, or, by rotating your mouse wheel, or, by typing into the rectangular box the number of points/vert’s you desire will automatically distribute around the circumference of the circle the correct number of vert’s with equal spacing between them.
Regarding the blocky car as you put it, for your second example. Firstly make a copy of the file, renumber it so that you preserve the original file. Then working on the duplicate file select the object/form listed in the properties panel on the right second panel down where it lists the object component tree. With this highlighted, select level 1 smoothing from the horizontal listing near the top of the properties panel. Now return back down to the second from the top tree panel mentioned previously and click on the small lighting bolt symbol, the result will be a reduction in what you describe as a blocky car. Is this the right way to make a smoother model ? Is WHOLE NEW CAN OF WORMS,