If you cannot do the 4x per day schedule because of work restrictions then by all means go with 2x per day, once in the am and once pwo. Try to coincide at least one of your injects right after your workout, preferably in the muscle just trained. You can even split up that pwo injection into two shots to hit each muscle equally.
I personnally take my gh on a similar 3x per week schedule doing one weeks worth of dosage in those 3 days. So instead of taking 6iu per day, I take 15iu pwo 3x per week. This is not an optimal way for those looking for fat loss, but for a lot of guys who have tried this protocol with me, the lean mass gains are far superior to the daily inject method.
Since I work out M, W, F I just take my igf on those days, with gh on those days as well. I would recommend if you take igf two times per day to make sure one of those times is pwo with your gh. The best method of taking gh is right after your workout, immediately, and then take the igf 20-30 mins after that.
The reason is that gh has a peak 1/2 life of about 16-19 mins depending on which report you read and since it has a conversion to igf near the end of that peak, you should inject your igf at this time to sort of super-charge your igf accumulation.
Now mind you, most of this is mere speculation by me during my research and studies, tested on me and some of my clients and found to work. I can't say this is gospel, nor do I have anything more to back it up than my empirical evidence but I am always researching and passing along things to you guys so you can try it and give me honest feedback. I am a scientist by trade and this is what I do.
Anyway, for the volume of igf recon I use 4cc per 1000mcg to I can have some additional water at time of inject since 15mcg is such a small amount.
I hope I answered all the questions, but keep shooting them at me so I can make sure you guys are covered.