Pines need full light when planted as seedlings, and they need the competition suppressed if you are planting a new stand or re-planting after a clearcut. I have planted pines since I was a kid and have had the privilege of replanting after stands I originally planted 30+ years earlier were clearcut. I have tried to introduce pines into existing hardwood stands and it doesn't work, they won't get enough light among standing trees. If you kill the standing trees, you will still have to come back and kill the seed bank. I have had success planting pines on skid trails through thinned hardwood stands, and along field edges of standing trees. In VA in order to get cost sharing for planting pines, they want you to cut in year one, come back and chemically kill the seed bank in year 2, and the replant in late winter/early spring of year 3, after everything else is dead. A couple of years ago, I was able to clearcut 6 acres in December, and convinced them to cost share on the replant 3 months later with a plan where I spot treated before the clear cut, and then went back and spot treated again after the replant. It worked very well. Here is a video I did explaining the technique: