I seal the inside and do it under tension so the stitch holes open as much as possible. Back in the day I used to use Sil-net but nowadays I use Permatex flowable silicone. I got mine at Canadian Tire in the auto section. Its flows well and gets into the seams. I have never found the need to use tape. The goal is to get some silicone into each stich hole so you don't need much and using tape may make you use more than you need. When its done you won't even see the silicone anyways. It helps to apply a little talcum or baby powder to the silicone once its cured so it does not stick to any other parts of the tarp when packed. That's just how I do it.
Don't let life get in the way of living.