Are you asking in regards for training bushido? If so, then no, using a shield won't affect your bushido gains. Since it doesn't affect the gains, there's no reason to equip the shield since it destroys your parry chance; you should only ever have a shield on with bushido if you are training parry itself.
And unfortunately, there doesn't seem to be any reasonable way to get bushido gains in the upper skill ranges. Past about 95 bushido, you'll be happy to get more then about .3 per hour with unguilded pets, and it's just as slow in active hunting. It's just too bad you can't set two pets together to apply momentum strike to that trick.
Once you hit that wall with LS, the best method I've found for gains is just going to champ spawns (avoid the caster tiers, especially if any cast mana vamp) and just spamming momentum strike. I gotta tell you, I'm -this- close to switching to a whammy temporarily to get bushido up.