Blood is tricky, its easy to make it look like a 12 year old has done it, but to make it look good takes special attention.

Red paint isn't what you want, you either want to use Blood for the Blood God from GW or Tamiya Clear Red, mixing these glossy blood colours with black or a red-brown will make it look older and stained, you shouldn't paint it, use stippling on the cutting edge and flick up on to the blade, or, for a splatter effect, try loading up your brush and the holding the brush up to you mouth and hold the model close to the brush, with the area you want to get splattered towards it, then, purse your lips and blow out really hard, make sure your paint isn't too thin for this or it will go everywhere