A general and efficient method for the preparation of bottle-brush brushes is presented via the combination of self-initiated photografting and photopolymerization (SIPGP) and rare earth metal mediated group transfer polymerization (REM-GTP). This strategy involves the creation of poly(3-((2,6-dimethylpyridin-4-yl)oxy)propyl methacrylate) (PDMPPMA) brushes and the successive conversion to surface-grafted macroinitiator brushes through the C-H bond activation by Cp2YCH2TMS(THF) complex. The surface-bound macroinitiator exhibits high activity and no initiation period in the polymerization of monomers following a group-transfer polymerization mechanism, resulting in the formation of side chains along the PDMPPMA backbone. The versatile approach is not only applicable to the polymerization of conventional MMA, but also active for the polymerization of heteroatom containing monomers, e.g., vinylphosphonate, 2-vinylpyridine and 2-isopropenyl-2-oxazoline, thus affording bottlebrush brushes which cannot be efficiently realized by conventional polymerization techniques.