We prove that if a finite group $G$ acts smoothly on a manifold $M$ so that
all the isotropy subgroups are abelian groups with rank $\leq k$, then $G$ acts
freely and smoothly on $M \times \bbS^{n_1} \times ...\times \bbS^{n_k}$ for
some positive integers $n_1,..., n_k$. We construct these actions using a
recursive method, introduced in an earlier paper, that involves abstract fusion
systems on finite groups. As another application of this method, we prove that
every finite solvable group acts freely and smoothly on some product of spheres
with trivial action on homology.
We show that every rank two $p$-group acts freely and smoothly on a product
of two spheres. This follows from a more general construction: given a smooth
action of a finite group $G$ on a manifold $M$, we construct a smooth free
action on $M \times \bbS ^{n_1} \times \dots \times \bbS ^{n_k}$ when the set
of isotropy subgroups of the $G$-action on $M$ can be associated to a fusion
system satisfying certain properties. Another consequence of this construction
is that if $G$ is an (almost) extra-special $p$-group of rank $r$, then it acts
freely and smoothly on a product of $r$ spheres.
Chain complexes of finitely generated free modules over orbit categories
provide natural algebraic models for finite G-CW complexes with prescribed
isotropy. We prove a p-hypoelementary Dress induction theorem for K-theory over
the orbit category of a finite group, and use it to re-interpret some results
of Oliver and Kropholler-Wall on acyclic complexes.