10
\def\mydefb#1{\expandafter\def\csname b#1\endcsname{\mathbf{#1}}}
\def\mydefallb#1{\ifx#1\mydefallb\else\mydefb#1\expandafter\mydefallb\fi}
\mydefallb ABCDEFGHIJKLMNOPQRSTUVWXYZ\mydefallb
New for Greek
\def\mydefgreek#1{\expandafter\def\csname b#1\endcsname{\text{\boldmath$\mathbf{\csname #1\endcsname}$}}}
\def\mydefallgreek#1{\ifx\mydefallgreek#1\else\mydefgreek{#1}%
\lowercase{\mydefgreek{#1}}\expandafter\mydefallgreek\fi}
\mydefallgreek {beta}{Gamma}{Delta}{epsilon}{etaex}{Theta}{Iota}{Lambda}{kappa}{mu}{nu}{Xi}{Pi}{rho}\mydefallgreek
$\bGamma\bDelta \bTheta \bLambda \bXi \bPi $
$\bbeta \bgamma\bdelta \bepsilon \betaex \btheta \biota \blambda \bkappa \bmu \bnu \bxi \bpi \brho$