Model validator should be extremely curious. He should never take anything for granted and should explore each and every scope of the model.Typical rule of the law is “Innocent until proven guilty”. In the validation exercise, it should be opposite, “Model is failed until proved pass”.
He should be patient and mature. He should understand that the model owner has developed the model after giving time of 6-12 months. On the other side validator has just 2 months (typically) to validate it and present the report. During initial days he will have gaps in his understanding. He might have to ask same questions again. The key is that he should be persistent in his effort of validation exercise.
The best way to deal with these situation is that each and every communications should be in written form. Try to avoid phone calls as much as possible. Even when there is a phone call, the minutes of the meeting should be written by the validator and shared with all the stake holders immediately.
Read the model development document and the written communication MANY times.
Ideally it is best that the validator handles one model at a time, but because of the resource constraints this is a luxury. But ideally he should not handle more than 2 models at a time.
It will be good idea if the validator explains his understanding through presentations to the other similar profile validators about the model he is validating. This will help him in two ways: first he will be able to summarize his understanding and recognize the gaps. Secondly other validators may bring fresh and out of the box perspectives and cross validate his understanding.
Model validation involves checking of conceptual soundness, outcomes analysis and ongoing monitoring analysis. Each of these three tasks have further subtasks which depend on the model. Model validator should develop a project plan with strict timelines before hand and work hard to ensure that these time lines are followed.
Lastly I would say that the validator should not wait till the end for the documentation of the findings/analysis, rather should document his findings from the very beginning. This will help him in keeping a record of analytical activities he performed during his validation exercise.