  A homogeneous nilpotent Lie group has a scaling automorphism determined by a
grading of its Lie algebra. Many proofs of upper bounds for the Dehn function
of such a group depend on being able to fill curves with discs compatible with
this grading; the area of such discs changes predictably under the scaling
automorphism. In this paper, we present combinatorial methods for finding such
bounds. Using this method, we give new proofs of some results on Dehn functions
of nilpotent groups, prove theorems on central powers and certain quotients of
nilpotent groups, and construct the first example of a torsion-free nilpotent
group of class 3 with a quadratic Dehn function.
