First of all, before we start: before you jump into the modifying your pedals, think about what you want to change. What is wrong in your pedal? Do you want something more or less? Do you want more bass or less treble? There is a difference. What do you think is wrong in your overdrive? Or booster? Or fuzz? Sometimes it makes more sense to sell the pedals you don't like to use. Because after you have modified them, it's much more difficult to sell them. Don't mod just because you read something from the internet. You should use these instructions only when you know what you aim to accomplish.
Internet is full of effect pedal modifications. Some are good, some are bad and then there are the expensive ones. In my view, information should be free. One can charge for the labour, but not for the information. So I don't recommend you to pay for mod instructions. I bet you can find all the information you need free in the web.
I try to provide some good, useful and/or worth to try modifications. All of these are well known, and none of them originates from me. Implimentation maybe "my own", but basics behind these instructions are not. I have picked these mods so that you don't have to drill any new holes to your pedals. I hate when people do that. Stop ruining stuff and stop making irreversible changes!
Now you may proceed.