Involved in the biosynthesis of the arabinogalactan (AG) region of the mycolylarabinogalactan-peptidoglycan (mAGP) complex, an essential component of the mycobacterial cell wall. Catalyzes the transfer of the first two galactofuranosyl (Galf) units from UDP-galactofuranose (UDP-Galf) onto the rhamnosyl-GlcNAc-diphospho-decaprenol (Rha-GlcNAc-PP-C50) acceptor, yielding galactofuranosyl-galactofuranosyl-rhamnosyl-GlcNAc-diphospho-decaprenol (Galf-Galf-Rha-GlcNAc-PP-C50). Thus, GlfT1 is the initiator of galactan synthesis, while GlfT2 continues with the subsequent polymerization events. alpha-L-rhamnosyl-(1->3)-N-acetyl-alpha-D-glucosaminyl-diphospho-trans,octa-cis-decaprenol + 2 UDP-alpha-D-galactofuranose = beta-D-galactofuranosyl-(1->5)-beta-D-galactofuranosyl-(1->4)-alpha-L-rhamnosyl-(1->3)-N-acetyl-alpha-D-glucosaminyl-diphospho-trans,octa-cis-decaprenol + 2 H(+) + 2 UDP Cell wall biogenesis; cell wall polysaccharide biosynthesis. Interacts with Rv3789. Is thus probably part of an AG biosynthetic complex. Was identified as a high-confidence drug target. Belongs to the glycosyltransferase 2 family.