If the aim is to complete the system at your place AND eliminate the moisture in the system AND minimise the time being spent at the shop for charging the refrigerant, then just hire a decent vacuum pump.
Hi Kaz
That's pretty much my goal (save time at the service shop). So I'm convinced to buy a vacuum pump and gauges/hoses instead of the nitrogen kit. At least I've found a supplier with reasonable prices (hard to find here).