For maximum stability, install grab bars on wall studs, as this will adequately support the weight. However, if you don't have access to studs, you can get by with wall anchors. If opting for the latter, choose specialty hollow wall anchors. 

Although they have similar applications, spackle and joint compound are not the same. Their primary differences lie in their composition, consistency, and ideal use cases.

Spackle is composed of gypsum and binding agents, making it thicker than joint compound. It dries quickly and is easy to sand, which makes it ideal for small wall repair projects like filling nail holes or patching minor damage.

Joint compound, also known as drywall mud, consists of limestone and gypsum. It is primarily used for large-scale projects, such as taping and finishing the seams on newly installed drywall. It tends to shrink more than spackle and can be more difficult to spread.

While both products can be used to fill small depressions and cracks, spackle cannot replace joint compound for taping and mudding new drywall. Conversely, you can often use joint compound for small patching jobs typically done with spackle.

There are six levels of drywall finish, from 0 to 5, that refer to the amount of work performed during the finishing process.

Level 0: Drywall is hung with no finishing work.

Level 1: Tape is placed over the seams between drywall sheets.

Level 2: A thin layer of mud is applied over the tape and screw holes. This level is common for utility rooms or walls that will be covered.

Level 3: A full coat of mud covers the screw holes and tape, but the surface is not sanded. This is often used in garages.

Level 4: This is the most common finish for visible interior walls. It involves applying two coats of mud over seams and screw holes, with sanding between each coat, creating a smooth surface ready for flat paint.

Level 5: This is a high-end finish for luxury homes. It includes full taping, mudding, and sanding, plus a final skim coat over the entire surface before painting.

If the holes in the plaster are small, you can fill them with layers of patching plaster until they’re filled. After it dries, you can sand the plaster and paint over it. If the hole is much larger, consider using bonding plaster first and then a layer of patching plaster, completing the process with sanding and a layer of paint.