The methods you describe are good ones and quite commonly used. There are many variables with producing good results from the bow. It would be beneficial if I could see your technique in action but I will take some shots in the dark here and hope to hit something for you:
First, make sure the bow remains in good contact with the strings as you draw the bow. Practice half notes on open strings and don't lift the bow to release; just stop the bow. Focus your arm weight into the string.
All too often when crossing strings, the bow begins to loose contact. Practice cross-string slurs and keep the focus as the bow moves from one string to another. Be sure to initiate the articulation from the shoulder and not the forarm or wrist. A good warm-up would be to simply lift your right arm so that it is straight and at right angles to your body and just let it come down under its own weight and hit your side. I worked with this in university with my teacher and it really helped establish that sense of focus that is needed for good tone.
Other considerations would be the equipment that you use. Ideally your bass should be set-up for arco. Some strings are designed specifically for this and others for jazz. I use Bel Canto strings and really love the response I get with the bow from these. I suppose I should have asked about your choice in bow as well. Do you use German or French? Either way, a good bow is essential in classical performance as well as the type of rosin you use. If the equipment is not set-up correctly or just not adequate enough, getting good results could be nearly impossible.
If your not currently studying with a teacher, it would probably be within your best interests to do so. Having a qualified person there to observe and correct could take care of a lot of issues in a shorter period of time. I may have an old beat-up copy of the Zimmerman around in my studio. If I can dig it out, consider it yours.
This is only bowing in a nutshell. I certainly hope it helps. Feel free to PM me if you would like to discuss anything in greater detail.