Hi John et al.
All my tractors are filled with anti-freeze because A/F contains some anti- corrosion compotent and it prevents oxygen, itself an agent for rusting, from attacking the vulnerable bits. it goes without saying that dripping pump seals don't allow this practice. As for mags. I just cover them up with a small rag and give the engine one pull-up every month or six weeks, this spreads the oil back up the bores without scraping it off altogether and excercises the impulse and points, it also eases the valve springs. American Boche mags are good in this respect.
As for the rest of the tractor I spray it all over with a mixture of Diesel and new engine oil with one of those plastic spray cans which you spray plants with. I don't cover the machine over at all, let the air circulate!