Problems near drywall tape....Please sustain??? I took the strips off the walls contained by my trailer and...

I took the strips off the walls contained by my trailer and now we are trying to video the joints. But we enjoy tried many different steps and nought is working too well. I am wanting to know the exact steps and what we entail to make it look right. When we sand the video ends up showing. We have tried sand to where to cassette doesn't show and it just doesn't look right at all. It is too gooey. So someone please tell me what we involve to do.
What site would enjoy this?
Answers:    Drywall has a taper on the brim for the tape and mud.In mobile homes we snap a queue 11/2 inches from the edge and cut along the flash with a cut-throat knife and afterwards remove the existing paper.Do this on both sides of the seam afterwards tape and mud and the seam will be flawless.
Staining Wood How long does it whip?
My parents also took the strips rotten of the walls. Instead of using tape on the joint they just used drywall compound on the joint and then sand them and you can't even tell.