The picts are often known as the "painted people". Wen it comes to wargames armies this is an atrocious pun indeed.
The prospect of painting an entire army filled with tattoos, warpaint, checked, striped and plaid clothing, and that wonderfully complex iconograpy including all sorts of complex birds, beasts, knots and spirals.
Fear not. There are several shortcuts and visulal cheats you can employ to ease the burden of painting Picts.
The first is fake plaid. Instead of trying to paint te full mix of colours and patterns in plaid simplify. Often a simple grid in a contratsing colour over a base colour will suffice. For a more complex pattern add a dot of a third colour at each intersection. You can also use one colour for the verticals and a different one for the horizontals.
Second, stripes are your friend. Stripes are muc easier to paint than plaids.
Third, keep the palatte simple. Earth tones, pale tans and creams, muddy greens, the occasional accent of yellow red or blue.
Fourth, trim is good. Adding a stripe of trim to a tunic hem, collar and cuffs can do as much for the look of the figure as a full on plaid tunic, and is much easier to paint.
Fifth, remember you are painting a warband. Using a uniform colour palette across most of the figures will tie them together. In a warband some figures can be quite plain, while others are exuberantly detailed, the viewer's eye will tend to average them out.
Sixth, shields help. Shields hide a fair bit of the body behind them. Also a shield presents a good surface to add a contrasting colour or pattern. Simple field divisions, spirals, and dots can give an impression of more complex heraldry.
Seventh, to dip or not to dip? Some like the "magic dip" of Minwax Polyshades Satin Tudor, or Johnson's Clear floor polish with black or brown ink added. Both of tese will provide instant sading and grunge to your figures. Some like the look, others do not. Try it on a spare figure and see what you think.