I still made it work. I got pretty good at reading the waveform preview, and was able to use that to figure out where to do cuts. I would apply effects and walk through frame by frame with the arrow keys to see how it looked. It usually took all night (and sometimes a bit of the next day) to render videos into 1080i, but it would render and the resulting videos would be fine.
Eventually I got a job and saved up and bought a decent CPU and GPU and editing got 10x easier, but I still kind of look back on the time of me having to make my shitty computer work with a certain degree of fondness. When you have a decent job with decent money you can buy the equipment you need to do most tasks, but there's sort of a purity in doing a task that you really don't have the equipment you need.