It hurts my soul to thin plants. The only solution I have to thinning is to make seed tapes in winter. You get paper strips and make some flour and water paste and your tweezers and seeds and glue the seeds onto the paper strips exactly how far apart they are supposed to be. I did this one year and I had good results.
The paper could be all the junk mail envelopes cut into strips or old files that you are getting rid of when you clean your filing cabinet. I always put that stuff in the compost anyway, so it's a win-win.