I'm relatively new to oil painting, having started with watercolours, a great British tradition. I understand that most artists use a combination of oil medium and solvent but I just can't get on with solvent - I reckon it's ok for cleaning brushes! My fellow students in the art class in Celrà use only solvent and it's horrible (try to imagine the Spanish pronunciation with a long rolled "rr"! The word is written the same in both languages) It's very strong and is normally purchased at hardware shops and I know of one art class where it is forbidden! "Aguarras", it's called (that's probably Spanish for aggravating, it's not good for the skin or the lungs). I recently bought a low-odour solvent (W&N Sansodor) and a jelly-like oil medium (W&N Liquin) from my favourite supplier in the UK (there's a link in my web-site). I rapidly gave up using the solvent but I love the Liquin - the art school teacher has been using it for years. I get there in the end!
My fellow students are not convinced, partly I guess, because they can buy a litre of Aguarras for next to nothing. But a bottle of Liquin lasts for ages so it doesn't work out expensive. I'll keep plugging away. I'll squirt a blob onto their palettes when they're not looking.
On the subject of paint surfaces, canvas is quite expensive in the art shops in Girona and, although much cheaper from the UK, the cost of shipping makes that expensive also. So, for a lot of paintings, I use MDF, either 4 or 5mm. This looks like wood but is actually compressed cardboard, as you probably know. I use 4mm MDF mounted inside my "Profile C" picture frame. It sits slightly behind the glass, making it look like an exhibit. I do the same with acrylics. MDF, the dust that is, has been described as being carcinogenic so I wear a face mask when cutting it.
I know people who paint directly onto MDF but I think a primer is essential - I use W&N Galeria Gesso Primer but there are loads of brands out there. The "tooth" which results is great for paint but not so wonderful for an initial pencil sketch. The surface acts like sandpaper and ends up muddied with graphite which then makes the paint dirty. So, rather defeating the object of the primer, I sand it down a little with fine wet and dry sandpaper - shock, horror! But this makes a superb surface for the pencil and, what's more, I don't use an eraser to make corrections which spreads the graphite around, instead I use water.
Once I'm fairly happy with the sketch (which is drawn as lightly as possible - I use an HB automatic pencil), I seal it with a light coating of Letracote or something similar. This seals the pencil which prevents it from contaminating the paint (it's not a problem with watercolours on paper, of course). I tried this with acrylic but it tended to be absorbed fairly quickly into the surface which gave a dull finish. But "E&OE" - errors and omissions excepted, as they say. This works for me but this is not really an art class so you must do your own thing. Having been a technical type of person most of my life, I'm fascinated by the "technology" of art: different surfaces, materials, mediums etc. Maybe, one day I'll get back to painting something (just kidding!). I used to go to the beach with my watercolours and just happily mix colours on paper without actually painting anything.
I am the only person that I know who works on a flat surface, even for oils. I have a studio easel but I use it to stack my recent paintings! Certainly all the other students in the art class use easels - I use a table! Maybe it's due to years of assembling small electronic components under the lamps which you can see in the photo. None of this expansive splash of colour for me, it's a precision job. I'm always being told that I should paint bigger but my scanner is only A4 so I can't can I? Actually, the largest painting I've done recently is the cat which you can see on my web-site . It's a 50x50cm canvas and, I have to admit, some of it was painted on a vertical surface. But only for a short while, mind you. I had to photograph it rather than scan it in order to put it on the web-site.