"And how long have they had to train Iraqi soldiers and police, many of whom were soldiers and police before? Over 2 years?"

I don't have a direct answer, but obviously it takes infrastructure and personel to train.
In the US:
"As of June 2000, State and local law enforcement agencies had 1,019,496 full-time personnel, 11% more than the 921,978 employed in 1996. From 1996 to 2000 the number of full-time sworn personnel increased from 663,535 to 708,022."
The number trained per year is:
"As of yearend 2002 a total of 626 State and Local law enforcement academies operating in the United States offered basic law enforcement training to individuals recruited or seeking to become law enforcement officers.
An estimated 53,302 trainees successfully completed or graduated from their training program. "
http://www.ojp.usdoj.gov/bjs/sandlle.htm

So with 626 enforcement acadamies we train 53,302 per year. One can assume that if we wanted to train 100,000 per year we could get more acadamies and require each acadamy to train higher numbers year [have over-sized classes and get more instructors, but this wouldn't be easy]. If we had to train our entire force [over a million personel, if wouldn't really be possible to do this because it would exceed our capablity- 100,000 might be doable but not a million- there is not enough infrastructure and not enough trained instructors. Training a million personel in 2 years would also be very hard to do. The US has more 10 times the population of Iraq, so roughly 1 million is comparable to 100,000. You are suggesting Iraqi police could be trained in 6 months, which equal to the US training at a rate of 2 million personel per year.

If you wanted to train quickly as possible so as to add million personel, the program would probably look like: 100k the first year, 200K the next year, 400k the next year, and hold at 400k per year rate, then subsequently reduce capacity. That would extremely difficult to do and very expensive, but that might be possible. But we certainly would not try to train a million new personnel within 6 months or within 2 years.