Harold,

Alot of us think that the XF-60 (dark yellow) has a bit too much of a green hue to it. I've had the best luck by using Tamiya's white primer as the base coat under it. This really makes it look more beige. By far the worst is the rust oxide primer, it makes the dark yellow look green, and consequently, has a significantly lower contrast in the three color ambush scheme. Right now, I simply use the gray automotive primer. It's cheaper than the Tamiya primer, and gives decent results. It's not as good as the white though.

Some of the guys in our club use XF-59 (desert yellow) as a substitute. Its a bit more tan, and less green. I haven't tried it yet, but I've got some ready for my next German summer camo job.