Your average japanese solo motorcycle uses 2 bearings per wheel with a spacer in between. The correct technique is
Use positive radial seal (2RS) rated bearings and remove one seal from them, fill with regular NLGI2 wheel bearing grease. Install the bearing, install spacer and fill the hub about 80% with grease, remove one seal from the other bearing, fill with grease pushing it into the races with the palm of your hand, install it open race facing into the hub. Install grease seal and you are done. The wheel bearings will last for a very long time, if you think that the grease has been compromised with water - then refill the grease or use waterproof synthetic grease.