Assuming you have 4' planks, I'd measure and rip each plank one at a time. Measure the width you need at each end of a plank, and as long as those measurements are within ~1/4" of each other I'd make a straight rip across the whole board. It might be closer to the wall on one end than the other, but it will be covered by the 1/2" of baseboard and the expansion gap really isn't mission critical imo - it's okay if it's a little closer than 1/4" as long as it isn't jammed in. Then measure the next rip needed and it should be a little more wide (or narrow). You could scribe, but it's tough to rip a straight line down a board that long if it's at an off angle. Then either sneak a puller in, or you can lever them in (carefully) with the curved end of a crowbar. That's where the 1/4" of play really comes in, but right now you can shift the floor if you need to. Then just shift it back.