100W Solar Supplement Enough?

[Sonnylu]

We dry camp a lot where there are restricted generator hours. We can usually run the genset for 2-3 hours. That gets us past the bulk charge phase and well into the absorption phase. How much solar capacity do we need to supplement this on an average day to get to the float phase (fully charged)?
100 watt solar panel? 200W?
I'd like to avoid being wrong by much in either direction. The batteries are 3xGC2 6V in a series/parallel 12V bank, with 460AH.
Thanks for any information you can provide.