Sanding advice for newbie

Most of the time detail will be sanded away when cleaning up seams and needs to be replaced with a scribing tool or a #11 blade depending on the detail. If it's raised lines then I lightly use a #11 blade to connect the panel lines. When this is done the plastic is raised a bit and restores the effect. You can also used stretched sprue and thin cement to restore the raised lines.

I like to use Tenax or Plast I Weld applied with a Touch N Flow applicator on seams then squeeze the parts together creating a thin ridge along the seam that when dry, can be sanded smooth to an invisible join reducing the use of fillers. 

Hope this helps.

I believe panel lines on kits are oversized in 1:72 and 1:48, especially for aircraft that will be painted rather than nmf.  Look at pictures of real aircraft, even weathered aircraft.  Panel lines- riveted ones, not removable panels- are very hard to see.  I prime with thick primers, that wash out panel lines almost more than treating seams.  I only worry about the lines on removable panels and cowl pieces.

It pays to mask around areas where there'll be putty/ sanding. It really reduces clean up and repair.

And practice dry fitting to identify problem areas before committing to glue. When gluing parts together, pay careful attention to the alignment of the join.  Get it perfect as possible.

Sometimes hairline ghost seams will appear regardless of the care you take.  I have found fine stretched sprue taken from the same kit is the best filler - same hardness as the kit plastic, does not shrink or flake like putty, sands and feathers better than CA glue.

Recently I have been following my own advice, and the amount of putty I use has dropped significantly.

HTH