Stock, the first one (.6) I explained either in this thread or a different one, I forgot, but you have to wait til they get close then jump up through the bomb changers and lay the blue bomb on them before you fall back through to the white bomb.
The second one (.

is really hard, the best I've managed on that level without an item is losing two lives. You have to be really quick, going up the middle path by kicking bombs up in each section to freeze them then jumping up to get to the blue bomb and then just jump round the whole level planting them everywhere and get all the enemies down to the bottom level.