Cheap white bristle brushes come in handy for nearly everything. The cheapest hardware store kind needs to be fanned out and all the loose bristles removed before using.
These brushes, including the foam brush, are good for gesso and varnish. Toss when done.
Dust is the enemy of a fine art painter.
I couldn't live without a Tack Cloth. I keep it near my easel an use it to remove dust and fine particles before and between painting sessions (when the surface is dry of course).
A tack cloth is made of cotton gauze impregnated with beeswax - and it mops up dust. Lightly wipe the surface of your canvas before painting. I am always surprised at how quickly the cloth gets "dirty" on an apparently clean surface.
Once the package is open, I store my tack cloth in a zip-lock baggie to prevent it from drying out.
Exacto and/or mat knife - who could function without one of these?
Rolls of masking tape come from the hardware store. It is necessary to keep a fresh roll around as they "fragment"as they age and it is nearly impossible to take a piece off the role.
Painters tape (usually blue - but not shown here) is a low tack (less sticky) tape. If you're going to use a piece of tape on a painting (for a short time only) in order to paint as straight line this tape is less likely to ruin the painted surface.
TIP: If ever you get a piece of tape stuck to something - oil will quickly remove the adhesive and allow you to remove the tape without harming the surface.
Shop Towels - they are blue & ugly - but completely lintless - much better than regular old paper towels. I buy them by the case.
Push pins are very useful in my studio.
My home-made Mahl Sticks (pictured above leaning against the painting on my easel) are essential to steady my hand when working on a wet surface that I don't want to touch. Sometimes I also use them when drawing so I can keep my surface clean.
I make my own mahl sticks of various lengths (only short ones shown). I buy dowels from the hardware store, stain them, and glue rubber cane tips on the ends (various sizes also available from the hardware store).
I keep a one pound tub of handy-dandy, super-duper, heavy-duty, industrial-strength HAND CLEANER near my easel. It is for removing grease, tar and oil in an automotive repair shop.
Sometimes I use Goop, but this one is pictured above is called Gojo. Lots of different brands out there - but they all appear to do the same job.
I consider this item a Studio (& Fashion) Essential.
Now I'm not a messy painter overall, but every now and then I get oil paint on a piece of clothing that I care about.
When I discover the "accident," I take a glob of cleaner and work it into the material from both sides of the fabric - don't be chintzy with the cleaner - use lots. If the oil paint is fresh you can immediately toss the clothing into the washing machine, with laundry detergent and wash as usual.
If the paint is old and dry, you can rub this hand cleaner into the material and let it sit for a while (for a few hours or even overnight) - then add a little more cleaner, work into the material (both sides) and then wash as usual.
It the paint still doesn't come out after one application and wash cycle - repeat the process....as long as you don't use the dryer to set the paint.
This (non gritty) hand cleaner usually comes packed in a tin or plastic tub - as a thick gel. In hot weather, it "melts" into a thick liquid. This does not make it any less effective.