I regularly toast 2-row and MO. IMO, a little goes a long way. Half would be much too much. Typically, I'll use no more than 5% of toasted malt in the grain bill.
Put the grain on a cookie sheet in a 275 deg. oven for 30 min, turning the grain @ 15. Allow the grain to "rest" for a week or two.
Your home will smell fantastic when you're toasting the grains. Good Luck.