an 8,9,11 sweep gauge should do the job ok,8 sweep is the shallowest gauge that I`d use to give a nice round bottomed groove,the shape and surface of the object being carved denotes which of the straight,bent backbent,fishtail etc is used.cutting of crossgrain just requires the tool to be extremely sharp so you don`t get breakout on the crossgrain and making sure the edge of the tool stays above the edge of the groove edge,another cause of breakout.There are lots of books on it,three good ones are,Carving on Turning by Chris Pye,How to Carve Wood by Butz and Woodcarving A Foundation Course by Zoe Gertner,cheers,
Eric.