Wipe-on or wiping varnish is just slightly diluted regular varnish Brian. So if you decant a bit into a jar and add some white spirit, you'll have made it yourself for less than you'd pay for it readymade in a tin. Common dilutions are from 25% to 50% although you can thin more or less than this if you like or as needed.
Brian18741":59chaneu said:
The few pieces I've made I've just finished with Danish oil but am I right in saying that Danish oil isn't a very durable finish suitable for the likes of a coffee table?
Poly should be noticeably more water-resistant and durable than any Danish oil but Danish oil can be used on a coffee table and provide the necessary protection.
Whether it's enough depends on a few things: which wood it's made from, whether coasters are used for sweaty glasses or hot mugs, how much knocking about the top might see, how many coats of Danish oil are applied. Also it very much depends on the Danish oil. There's no set formula for it so every make is different and some are much better than others.
Brian18741":59chaneu said:
And do you apply a few coats of oil and then a coat of polyurethane on top or just a few coats of polyurethane and be done with it?
You can oil first and then varnish, that's not uncommon these days. This would be oiling with boiled linseed oil or something like it, not Danish oil which isn't actually an oil but a blended finish (it's generally a mix of oil & varnish & white spirit).
Whether oiling first is worth it depends. On some woods it makes a difference in how much the grain is enhanced, or "popped", but on others there's no noticeable difference so it's very much not something to do all the time unless you don't mind the added day or two in finishing time.