Being on my third airbrush I have this advice to give:
- while it can be used on 28mms it is more appropriate on vehicles and for weathering; I never use mine for base coating since it is much easier and probably no more expensive to use a spray can
- buy quality. If you want one fork out as much as you can afford; you generally get what you pay for (if you turn to reputable vendors)
- be prepare to spend a bit of time to master it; it is a tool not a magic wand and all the "configurables" can make it a bit confusing to use
- get all the space and tools needed; you need high pigmentation, lump free, quality paint, som sort of spray booth, lots of pots and mixing jars and large sheets of paper to calibrate and practice on
- clean properly; acrylics dry fast in a airbrush so have plenty of cleaning fluids ready
That said and as you probably know, it is a lot of fun and can give great looking results once you master some basic techniques
Edit: Oh, and about that ebay kit: I don't see why you would need two double action spray guns: I'd say you need to keep one busy and moist throughout one paiting session. Other than that I think the guns look ok at a glance. The compressor may be on the smallish side which may lead to uneven air supply/preassue. But it may be OK for the price and for your entry level, if you understand what I mean.