Calculating Synastry House overlays by hand

I am hoping i'm not asking a repeat question (if indeed I am please shoot me to where I can go) I am trying to do house overlays by hand. When calculating which of my partner's planets fall on my various houses what formula do I use? I do not want to use an online program. Any help would be greatly appreciated.

For instance, I found this:

"Identify the sign and degree of each planet in the first chart, and find the house where that same sign and degree are in the second chart. That is the transposed position for that planet. To illustrate: If your Mars is in the third degree of Gemini, and that degree of the zodiac is in your partner’s sixth house, your Mars falls in their sixth house– regardless of where it is in your natal chart. "


This is where I am confused. For example, his Sun,mercury,venus,saturn (all in Cancer) falls on my 4th/5th houses (cancer) ? Just by sign alone? Do the degrees have to match as well?

Please help. Thank you again.