i assume you mean 'in reverse direction' (hehe) Seriously tho' - last year I met an Australian couple on bikes in Sanabria who, having finished the CF (including to Finisterra) in the regular direction, were doing VdlP in reverse direction - they were really 'hanging out' to get out of the hilly part of VdlP!
And in Laza I met one German pelegrino who was walking 'in reverse' from Finisterra - he said he was finding it difficult to see the yellow arrows and had consequently often strayed off the marked 'way' - but he was enjoying the challenge. A few times on lonely stretches on the VdlP where there was only a solitary arrow to be seen (from the 'regular direction') I checked out how visible they were from the reverse direction - I guess the guy had a point - they weren't immediately visible and I guess it would easier to miss one or two.
If you're starting in Santiago, not walking home from the pilgrimage, then staying in Albergues might be a problem. Waymarking, as it's to direct people from the other direction, might be difficult to follow. And August will also be hot, and getting hotter, as you travel south.
consider walking from Santiago to Oviedo, the primitivo, even part of the north route, the province of Galicia has really worked hard at marking the trail. it is a reverse BLUE arrow. met a guy walking backward on the camino norte, he was going back to france. alittle more difficult.