Every printer has a USB connection plug, that receives X,Y,Z-axis control commands, and gcode print instructions, from a controller/slicer program. That program does not help you level the plate (directly), it only moves the nozzle around , so you can manually make adjustments to the bed.
http://www.thingiverse.com/thing:630655/#files This is a ONE layer test. Choose the “spiral test file” that fits the size of your bed.(75% of bed size will be fine). Watch for a good/consistent “squish”, of the filament, to the bed plate.
Once you understand what you are trying to accomplish with this test, then you will be more comfortable just using skirts around your normal print objects, just to double-check your bed for level, before the actual print starts.
You will never/can’t bump the print, because the adjustments are made on the 1st layer, before the print ever starts.
As an additional note: Since you mentioned this is a self built printer, please use a square, and make sure that your machine is square, in all directions.
If it is not, you will never get the bed “ON AN EQUAL PLANE WITH THE X and Y GANTRY(s)” / (level).
What I am trying to emphasize, is that there is really NO such thing as “level” (it is just a generic term)
A printer can print on it’s side, or upside-down, as long as everything is “square”, and the bed is on an “equal horizontal plane”, with the nozzle.