If you wish to learn drafting related to the industrial disputes, then you need to work in lawyer's firm who handles labour cases.
Even before learning drafting, you need to improve your grammar. The grammatical mistake in the heading of your post is prominent enough to make this recommendation.
Drafting is complex activity and it has to be learnt under the guidance of expert. The basic principle of drafting is that one should not contradict with oneself. Secondly, occasionally seeds of failure are sown in poor drafts. To avoid all this guidance of expert is necessary. These things cannot be learnt through some academic course or online training.
In stead of providing the relevant information in piece meal relating to any query we raise in a public forum, it is always better to give them at a stretch with the situational need for the answer particularly when the query is of general nature. At times we have to answer the questioner rather than the question when a trade union leader happens to be the one. Again it is not known whether you are a plant-level union leader or a full-time unionist. Whatever it be, the advices tendered by our learned friends M/S Dinesh and Srinath are quite apt and essential to any person taking an active role in industrial relations. For a trade union leader it is all the more important to have a thorough knowledge of various labor laws coupled with relevant case laws and enquiry proceedings. Next, a trade union leader should have effective communication skills. If you know when and how to say "NO"in negotiations, " YES " will be the automatic response from the other party to your proposals in a conflict situation. When thorough knowledge of labor laws and communication skill are in your repertoire, drafting will flow out spontaneously.
As per the comments post by you, it is clear that you are working in the company and held post of Union Leader. As rightly said by Mr. Srinath your replies are more restricted to replying to Show Cause Notices/Charge Sheets, memo etc. Most of the Trade Unions has their own personal lawyer who helps them to do so in legal manner. Thus, you may hire one lawyer who will be doing this job.