Thats how i started ,found one called Daniel R6 on this forum , and together with a layout where i knew how i saw my "ideal controller" , i just started tinkering.
It's easy , open the touchosc editor on ur pc , set it to the dimensions of your device , portrait / landscape mode .
Then right click , pop up menu and put push buttons , toggles , faders , XY pads.
Coloring & labels are handy , you can edit these things in the left panel.
Then it's just looking in resolume what the adres is for what u want and copy paste that to the knob/button/fader in touchosc editor.
Open resolume , go to shortcuts , edit osc , everything turns purple.
Click on anything you want to link , and in the "shortcuts panel window" which appeared when you hit edit osc, you'll see an input adress : /composition/layers/1/video/opacity.... something like that.
Copy that , select a fader in touchosceditor , in the left panel , middle part "OSC" , uncheck the 'auto' box and paste this adres there. That's it.
Then you can go deeper with adres + commands , and other magic tricks , there is a nice section about it on the resolume support pages.