for pullup practice, I have a downstairs bar in the rafters along with a set of rings, and a bar in my bathroom door. The bathroom door is visible in the main area of my house, just off my closeted laundry area and master bedroom and that is the one that gets used for GTG.
Basically whenever I walk by and see the bar (visual cue), or use the washroom,throw in laundry or go into the bedroom, I try to do a pullup or variation thereof, such as doing a negative, or jumping to 90 degrees at the elbow, and pulling the rest of the way (my weaker part of the move). I have a Post-it note by the bathroom door, to keep track of my volume for the day and have dates on it and make checkmarks. When I hit "x" amount, I am done for the day.
I don't so much keep track of how much I have rested between sets (generally is at least 1/2 hour I think if not more), but my accumulated volume in the day and have set goals for how much volume in # sets per day I am doing in a week (found out pretty fast recently that 8 slow negatives in one day plus a set of 5 rows on rings in a --for me--fairly difficult foot stance in between every set of getups in my S&S session was a little much) Because I work odd shifts and hours, I need to squeeze these in when I can vs setting a timer and doing every morning....which is what is so great about GTG methods.