You will be fine giving nutes in flower even if you didnt use any in veg.

Depending on your system, FF makes two different veg nutes. Growbig and Growbig Hydro... should be self explanitory.

As far as the feeding schedule. Go to the fox farms website. There they have hydro and soil feeding charts for their products. From experience I would use HALF the dose they suggest and also use in this order, Feed, water, water, feed. Meaning after your first feeding give them clean water for the next two waterings, then feed again on the third.