The tools pictured above are ideal for on-the-go sketching on postcards, pocket sketchbooks, and 7" X 10" watercolor blocks. Shown closed and ready for travel in the picture below (clockwise starting from top left corner): Winsor & Newton Cotman Water Colour Field Plus Set , Pentel Vacance Water Color for Artist, Yasutomo plastic folding palettes filled with assortment of Holbein, Daniel Smith, and Winsor & Newton artists watercolor tube paints, Derwent pencil wrap loaded with watercolour pencils, Cotman 15 water colour postcards pad, Hand Book 5½" × 5½" Artist Journal, Moleskine 3½" × 5½" watercolor notebook, and Faber-Castell Albrecht Durer Aquarelle Sticks set of 20.
The Field Plus Set is a nice gadget, but a tad on the bulky side especially considering that a good waterbrush renders the waterbottle feature somewhat superfluous (at least within an urban environment where bottled water or a sink are usually not too far away, but I guess a dedicated canteen would be an asset out in the wild). The cakes from the original Cotman pans have been replaced with artist grade tube paints, but they were inexpensive beginner paints suitable for practice and sketching. The Plus cartridge system is convenient for swapping paint pans quickly and keeping each color separate from the rest preventing contamination.
The plastic folding palettes are inexpensive, light, offer plenty of large mixing areas, and can be loaded with any selection of favorite tube paints. Some green and blues (phthalos) pigments unfortunately tend to stain them permanently.
The Derwent canvas pencil wrap is a pretty convenient way of carrying pencils and keeping them organized while working anywhere. Although depending on the finish and diameter of the pencils (especially those smaller than 10 mm), there is a tendency for some to slip out of their holding loops and fall off the wrap. The revised model featured in some British websites has corrected this flaw, but I have yet to see it on any US retailers' sites. As for the watercolor pencils, I prefer the brands that color code the entire pencil barrel for ease of identification and that yield bright color washes. Currently my favorites are Faber Castell Albrecht Durer watercolor pencils and Caran d'Ache Supracolor Soft Aquarelle Pencils. Derwent watercolour pencils perform well and are readily available in local craft stores like Michael's, but I dislike their current color-coding system of only marking the pencil end and their slightly duller and "milkier" washes. Derwent did release a 36 watercolour pencils 50th year special edition box on 2003 for which they painted the entire barrels (see picture with open pencil wrap which incidentally has traveled with me in my carry-on bag on many flights), and some of them can still be found in retail stores.The 4"×6" postcard format is an ideal working size for various reasons: requires little paint and water limiting potential mess, can be completed on a short time since it usually dries quickly, and the resulting sketches can be mailed to relatives like proud grandparents that would likely treasure the works of their fledgling Van Goghs.
My original set of 20 Faber Castell Albrecht Durer aquarelle sticks has been a constant fixture in my vertical messenger bag or travel backpack as my preferred source of convenient and seemingly ever-lasting watercolor pans. I have often shared it with my nieces, as they learn to paint with brushes and explore watercolor media. It has certainly outlasted a set of Cotman water colour half pans, that my older niece managed to use up on a single afternoon with a 1/4" wash brush and buckets of fresh water. While she has learned to blot the excess water from her brushes on a paper towel after cleaning them, she still tends to destroy conventional watercolor pans with her vigorous scrubbing (which is also why I still only let her borrow synthetic brushes for now). The aquarelle sticks have proven to be quite resilient and have survived several kid painting sessions. Unfortunately they seem to have been discontinued in the US, but they occasionally still pop up in clearances and close out sections. I have been lucky to secure several kits and tons of open stock from art supplies sales in the past couple of years.
For larger scale paintings, traditional supplies (watercolor tubes, sable rounds and synthetic wash brushes, and large water buckets) might be more efficient so long as proper care and closer supervision are taken.