I was looking for an answer to the same question, but my search to answers proved elusive. I went through the offer letter and here (PEL Print.pdf (1.2 MB)) is the edited relevant portion which you can go through to get your concerns answered.
In short, an application can be submitted through plain paper as well. The details are on page number 409. In addition to what has been listed on this page, there are few more details which need to be submitted. I have written it down on a paper to which I don’t have access until the end of the day. I shall edit this post after I have access to it.
In addition to the details listed on page no. 409, the following are to be provided as well in the plain paper application.
Bank A/c Number
and the letter has to be posted only from an Indian Address and not from overseas address for legal reasons.
I communicated with the registrar and their reply said, on their website the same form will be available after issue opens, which is 12th Feb. I will wait until Monday to see if that is going to be helpful. If not, I will draft my own letter and proceed.
I have ignored the ASBA option considering other issues. Probably you can consider that if that is convenient to you.
An alternative option which I am looking at is if the price goes below 2500, I may give up the hassle of applying for the rights and load up the shares from the market itself. Hence I posted the question few days back on this thread? The idea behind this is to be not penny wise considering some of the constraints I have.