Best Way to Test Glow Plugs?

[jake12tech]

Okay, looking for the best way to test glow plugs without pulling them out on my 92 300D. If I pull them I'm going to replace them, it has 310k miles on it. I was wondering if the method and readings I was getting is correct. I tested each plug with a multimeter set on the OHM setting and got 9-10 on all the plugs except one that read six ohms. is this right? Is there a better way to figure out which plugs are out? I'm getting cold start misfire and white smoke, just like glow plugs. There's a lack of cylinder heat on cold start. Once its warm, no smoke. The engine has good compression for its age, its well broken in.