Why would you want to use TIFF instead of JPG?
There is no reason to do this.
You already put comments on a photo indelibly by using MS Paint.
There is really no standard procedure for recording comments on digital
photos. Many ways to do it.
I would recommend you download the free software:
www.irfanview.com
and download all the plug ins available with it.
To add text, open Irfanview, open the file you want to add text to, click on
the help files, index, text and follow directions. You will see lots of
options. Easier and more versatile than MS Paint.
One more thing. Do not add text on your original photo files. Make a copy of
the original file and then add text to the copy. This way you can always go
back to the original file and change things.
To make a copy, right click on the file (or for a group of files, select
them and then right click on them). After you right click, click on Copy on
the opening menu. Then click on Edit on your top bar and click on Paste.
This will add files in your folder, same name as the original files, but
with the word "Copy of" in front. You then open "Copy of" to add your text
on the photo.