The original softshell idea was modelled on what the Inuits wore for centuries, being a sort of synthetic animal skin, the pile being the fur that holds the warmth both wet and dry, and the outer shell or membrane being the skin that blocks the wind and snow. By having this single layer, no base, mid and shell, they could dump heat quickly, and so avoid sweat build-up (sweat being the real killer in cold temps). The Inuits did not wear these kinds of clothes in wet weather as they’d quickly rot away and so worked best in sub-zero conditions, which is where all softshells tend to work best. In wet conditions, they would use skins without any insulation, and the Aleutians even had the first waterproof breathable clothing, using the intestines of seals to make long jackets. But it’s worth remembering that native peoples were far tougher than us, and there are accounts of Patagonian Fuegians sat naked in canoes with snow settling on their shoulders (although often being naked is warmer than having wet clothes on).
For really wet conditions you need to borrow some soft shell thinking and employ more traditional skills and fabrics, and I found having done a lot of sea kayaking trips over long distances helped inform how I dealt with wet trips on land.
For single-day hikes you can really wear what you want, but you’ll want a fully waterproof shell (Gore or eVent), plus gaiters, good boots (wellies can actually be great for short hikes), and a hat to keep the hood away from your face. It may sound stupid but an umbrella can be a fantastic bit of kit as long there’s not wind. Under this, you need to make sure you don’t get too hot, as you’ll get sweaty, but know you will get wet if out all day, so wear clothes that don’t get cold and clammy (cotton). If it’s a big day then dressing as if you were going for a long run can work pretty well, with wicking leggings or even running shorts and a thermal top or two workings well. The big issue is when you stop, so make sure you’ve got a dry bag full of extra layers. Being comfortable is a very relative term, with being able to handle discomfort being a better guide as you will get damp. Always make sure you have dry clothes in your car.
For longer trips, you’ve got a different problem as nothing tends to dry, so you need to use a more maritime technique, having a dry and a wet set of clothes and changing between them from day to night. These dry clothes need to be as light as possible and their dryness kept sacrosanct. This layer does not need to be as warm as your daytime layers as you’ll have your sleeping bag to keep you warm, but something like flip flops, shorts, thermal top and light fleece can work, while others will take crocs and socks, long trousers and a maybe a light synthetic or down duvet for colder wet conditions. One good system if bulk and weight it critical, but you need some good performance, is to use a ‘zoot suit’, a suit made from parachute silk and used by Commandos, giving them a dry layer that took up little room in kayaks. The modern zoot suit would be a Pertex top and bottoms, which even when worn next to the skin can work pretty well (think Fuegian Indian). If you need to go around camp then you can wear your waterproofs, as the dampness won’t really wet your dry layers, but ideally, once you get changed you’re changed till the morning. One good thing about a zoot suit is that it dries more rapidly than any other clothing as it holds very little water, meaning if it does get wet your body heat will dry it out.
Changing into wet clothes can be grim, but hopefully, they’ll just be damp. It’s hard to dry stuff when camping with it being dry and sunny and windy, but a clothesline inside your tent can help (extended porch tents are great for this). Another option is to lay your damp items on top of your sleeping bag, then place your shell over it, or even sleep on top of your clothes, placing them under your bag. If you want to take the risk and your clothes are only damp then you can wear a damp thermal over a dry one around camp and in the tent, as this will dry it out, especially if you sleep in it (just make sure it’s damp and not wet).
It’s obvious but don’t be weak and wear your dry set the next day, unless it’s your last, as then you’ll really be in for a grim time. Also remember that on very long trips like this, the dirtier the clothes get the harder they are to get dry, due to body salts, so if this is the case try washing every now and again.
Brand wise seeing as I work for Montane it’s got to be montane, and they have a lot of very good softshells, both the Extreme range for full-on winter and expeditions, and lighter clothing for warmer temperatures.
For what I do, I avoid membraned fleeces, and prefer fleeces with a good loft to density, a pile/fury side next to skin, then wear a Pertex style wind shirt over the top if it’s dry, or my waterproofs if it’s raining. If find this system works well for very wet climates, as they dry faster than a membraned fleece (on a washing line or close to a fire), plus doesn’t get too hot, which is the key to staying dry(ish) and comfortable(ish).
If all else fails, try killing a seal and sew yourself up something a little bit more old fashioned!