  We described details of a method to estimate with good accuracy the mosaic
angle distributions of microcrystallites (platelets) in exfoliated graphite
like Grafoil which is commonly used as an adsorption substrate for helium thin
films. The method is based on analysis of resonance field shifts in
continuous-wave (CW) NMR spectra of $^{3}$He ferromagnetic monolayers making
use of the large nuclear polarization of the adsorbate itself. The mosaic angle
distribution of a Grafoil substrate analyzed in this way can be well fitted to
a gaussian form with a $27.5\pm2.5$ deg spread. This distribution is quite
different from the previous estimation based on neutron scattering data which
showed an unrealistically large isotropic powder-like component.
