lately, i've been using ink for washes. I found a nice pen-refill
type of container with non-opaque sepia ink and thinning that with
water and some ivory dish soap (thinner than most others and doesn't
smell like a damn lemon tree...) makes a really nice wash. It
doesn't form rain spots and doesn't attack the acrylic. I've
actually used it without a gloss coat on some figures but took care in
applying it. The other nice thing about the mixture is if you
store it in a jar the pigment won't settle to the bottom like it's done
for me with oil colors and even enamels. Plus it's zero-toxic.
I've actually sat down with a test piece painted with acrylic+future
and rubbed it with q-tips dipped in different solvents.
Ironically, brush cleaner (i think it was Testors) was on par with
water. The strongest ones (ie one swipe and it runs) were
isopropil alcohol and mr color enamel thinner (that stuff is REALLY
strong). Most enamel thinners were so-so but, having made a wash
with floquil thinner, i happen to know that it makes a future coat curl
up into orange peel. I used a brush cleaner + enamel/oil for a
while but now i think i'll stick to the ink+water+soap concoction.