I do all my own work on my bow and I don't have a bow press. I'll share my method, with a firm "do at your own risk" warning. Good to know tho in case you are on a hunt and need to do a quick fix on your equipment and a bow press is not handy.
2 people are needed
One person draws the bow back being extremely careful not to dry fire or let go of the string.
While the one guy holds the bow at full draw, Person number 2 inserts a screwdriver or anything that is strong amd fits into the closest spoke in the BOTTOM cam BELOW BUT CLOSEST to the the limb. Insert the screwdriver so it's sticking out both ends past the limb, and have the person holding the string GENTLY lower the string until the screwdriver contacts the limb.
The string will become limp to do what you need, then line it back up on the cams and pull it back again while your buddy removes the screwdriver again being careful not to dry fire, let the bow back down gently.
Again... Probably not the best way to work on your bow, but it will get the job done if you need to know this sometime in your life.
Here's a drawing to help see the process.