hmmm personally since ur sanding it down, i ahve some experience with body work but not too much, so someoen can correct me, since ur gona get it repainted so this wont matter so much
sand down to metal around rust area about 1ich around, if it is straight through, weld a peice metal to it
if it is surface rust, grind all rust spots off, and try see if u can grind from back make sure its all gone, or its gonna come back, then put some bondo and putty on top of it and get some cheap red paint and paint it till its rdy for body work, or jsut primer the spot,
this is just basic steps, but ask around for a detail step
thsi jsut let u know wats up with rust and rust is like cancer,it spreads, treat it earlier the better good luck my friend, i love honda but that only thign i hate about it lol
progress of $50 dollar paint job
http://www.honda-tech.com/zeropost?cmd=fshow&id=84