There is nothing that prevents you from training trainers as long as there is a structured approach to you training the trainers and the trainers training other employees. An essential requirement for any "significant" training, some may say any training delivery is the potential trainers presentation/training delivery skills. There are some generic courses for this. I feel that sometimes, we place excessive importance to accreditation, certification and so on by recognised organisations instead of applying sensible health and safety requirements to training. Firstly, there is no explicit statutory requirement for trainers skills in general health and safety legislation, although some legal beagles may advise that accredited/certificated training from reputable organisations will serve as more robust defense against civil claims. What you need are potential trainers with decent presentation/training delivery skills. Then you need to structure the trainers training content and also the final training content for the potentail trainers training employees. What is critical is the method you will use to assess the effectiveness of the training, both for you training the trainers and then the trainers training the employees. This can be done using a combination of practical and written "tests". The onus is on your self to determine whther you want to do it yourself if you feel your are a competent trainer or use external experts. You will need to suport your trainers if you do it internally, but there are advantages as you know your activities and the type of manual handling involved better than external experts! You may want to determine whether it is more cost effective to use your time for this or to get an external trainer from a reputable organisation. If you keep an audit trail of the above structure, you should be able to demonstrate that you had a sutable training "system" in place.