HI, Cody -
1. I agree that the .5 tip will be problematic in the smaller scale.
2. Even with a smaller tip, you'll find that LOT'S of practice and experimenting with pressures, thinning ratios and distance from the subject, will pretty much determine how you go about it.
3. In my experience, (fairly limited,) acrylic can be a bit touchy. But when I found the right thinning ratio and the type of retarder that reduced tip dry, I found that I like it as well as enamel. I do think the advantage for acrylic is the tougher finish.
I found myself in the same boat as you, what got me comfortable was practice and lot's of it. I know paint is pricey, but the satisfaction of being comfortable and proficient at camo painting, makes the investment of time and $$$$ spent on materials well worth it.
I'm not familiar enough with the Iwata brand to know if you can simply change the tip and needle, to utilize a .25 or .30 model. If so that would be a good place to start, likely you would find the smaller size to give much more precise control.
Check Don Wheelers website, (Don's Airbrush Tips,) he may well have an explanation as to the possibility of a modification of the A/B. I wish you good results.
Patrick