Fairly confident that guild support will only help when synthesizing something that require training (especially if you don't have it) and facility. It certainly does not virtually raises your rank. Case in point, I was making buffalo leather dye (a 29-30 recipe) at 25. My success rate is pretty much the same with or without the master support.
No it doesn't help with training, you need Training Book for training. I can complete 2 out of 7 stat rings, with 5 bothers on 100% progress 0 durability, but I can't get past 60% on 6 attempts of Dark Silver Circlet, they both require minimum rank 30 Goldsmith to even attempt. The difference is, I have Inlaying Training and not Gemcutting Training, both used Master Facility.