I am a dual journeyman aircraft and automotive mechanic, as well as a certified x-ray, ultrasonic, eddy current, magnetic particle and liquid penetrant NDT inspector.
I became a certified X-ray weld inspector in 1977. I have rejected 1000's of welds over the last 30 years. I have taught 1000's of student inspectors how to visually inspect a weld, BEFORE they waste the customer's time and money by X-Raying it. It costs between $300 to $600 per foot of weld to x-ray it - if you bring it into their shop - 10 times that, if they have to drive out to your place.
You cannot possible expect to have any success with an old buzz-box farmer welder, without completing a whole lot of maintenance and replacement of worn parts - starting with new cables, ground clamps, rod holders and ovens, contact points, new DRY welding rods, preferably using a 6011 root and filling with 7018 and that depends upon what you are welding and the parent metal composition/alloy material. Actually, MIG/GMAW is best for making root passes, because you would have fewer stop-start problems, or defects.
The first thing you need to research is common weld procedures, at any welding company in your area. They explain in precise detail every possible aspect of how to complete a successful weld.
Then practice welding sample pieces for at least 8 to 10 hours, using different thicknesses and weld positions, before you ever actually weld something important. I always chop up the weld samples and rip them apart whenever possible, to make sure there is complete penetration and no included weld defects ie: porosity (caused by water), slag inclusions, plus at least 30 more potential defect problems.
It has been my experience that welding is one of the most difficult learning processes in the industrial trades field.
Some people are just naturally great right from the start and others can't seem to lay a decent bead if their life depended upon it.
If I ever caught some idiot welder soaking his rods in water, he would be down the road in one hell of a hurry and blackballed in my petroleum industry.