body
 

what whould be better for patching rust Bondo Body Filler (Short-strand fibreglass) or the regular body filler. and i am cutting out metal and adding metal what will be a good filler to fill in the joint

Cutting out metal and welding in new stuff, I asume. Beat it as close as possible and use a quality filler. Either plastic or metal type. You should only need a slight skim to even things up.

where not welding it since we don;t got a welder where puting rivits i have no idea how to spell it

if your gunna use bondo use the fibreglass ones they are waterproof and is tough unlike regular bondo. The downside is takes really long to sand but is worth it when your done

Go to a good body shop supply store. You can get adhesives (2 part epoxies) that are as strong as a weld. You can use them in spots where it is not structural. Attach the new metal with the epoxy and a couple of screws or rivets to hold it in place while it sets. Then just use enough filler to finish.

You can use the stranded 'glass as it covers a hole better, but it will likely just fall out as more rust appears later.

next question is i finished all the metal and bondo now i have to prime it do i prime it and use sand paper after every coat and what grid do i use if i have to and what about after paint

after the first coat of primer, check for imperfections, if none, then lightly sand the primer with 600 grit until smooth, then paint

if i see lines what can i do