How to Use the Brush Tool in Photoshop

The Brush Tool Size and Hardness Shortcut

Press B for the Brush tool. You can set size and hardness from the options bar or by right-clicking on the canvas, but the shortcut is far faster: Ctrl + Option + drag on Mac, Alt + right-click + drag on PC. Drag left and right to resize, up and down to change hardness, all while watching a live preview of the brush. This is the single most useful brush shortcut there is.

The Brush Tool: Opacity vs. Flow

This distinction matters more than almost anything else about the Brush Tool. With Opacity at 10%, one stroke lays down 10% and going back over the same area in that same stroke adds nothing – you have to lift off and start a new stroke, and each pass leaves a visible edge where the passes meet. With Flow at 10%, paint builds continuously as you work back over an area, exactly like ink from a marker. That makes flow the natural-media choice and the better default: leave opacity at 100 and lower the flow, and you can build an effect from invisible to full strength with beautifully smooth transitions. Type a number to set opacity (5 = 50%, 0 = 100%); hold Shift and type to set flow.

Pressure Options and Tablets

Three icons in the Brush Tool options bar tie pen pressure to opacity, enable the airbrush (which keeps building as long as you hold the cursor in place), and tie pressure to brush size. A pressure-sensitive tablet is a genuine upgrade for brush work – thousands of pressure levels instead of a mouse’s on or off – though it takes a month or two before it feels natural. Once it does, most people never go back.

Using the Brush Tool on Layer Masks

This is where the Brush tool earns its reputation. Add a Curves adjustment layer and brighten the whole image, then press Ctrl/Cmd + I to invert the mask so the effect disappears. Now paint white with a large soft brush at low flow over your subject’s face and the brightening appears only there, building gradually as you work. The same approach with a Hue/Saturation layer – small brush, white paint, over the irises – adds saturation and lightness to the eyes alone. White reveals, black conceals: that pairing of brush and mask is the foundation of almost every effect in Photoshop.

Building a Snow Brush for the Brush Tool

Open Window > Brush Settings. Under Brush Tip Shape, increase Spacing until the stroke breaks into separate dots. Under Shape Dynamics, raise Size Jitter, Angle Jitter and Roundness Jitter so every dot differs. Under Scattering, enable Both Axes and raise the scatter and count so the dots spread across the frame. Under Transfer, add Opacity Jitter so some flakes are fainter than others. Pick a near-white color sampled from the photo – pure white rarely matches – and paint, varying brush size for flakes at different depths. Save it with the panel menu’s New Brush Preset and it waits at the bottom of your brush list forever.

The Brush Tool Quick Reference

• B – Brush tool
• Ctrl+Option+drag (Mac) / Alt+right-click+drag (PC) – size and hardness
• Number keys – opacity; Shift + number keys – flow
• Prefer flow over opacity for natural, buildable strokes
• X – swap foreground and background colors while masking
• Window > Brush Settings – jitter, scattering and custom brushes