Used oil based undercoat all over kitchen walls

Yes you can paint over it ok itwill just take a lot longer to dry its meant for woodwork and metal but i used it to kill grease stain and damp stain so really good but how ever dont recommend it to use on walls

Genrally in a kitchen dependant on how many years ago since it was painted, if its greasy then a sugar soap solution to wash off any residuals on ceiling and walls would be applied first, besides that I would not use old undercoat supplied by the customer anyway, if any stains remained then white undercoat or suitable stain block would be applied and left to dry, then apply two coats of white emulsion or washable emulsion to the customers choice on all walls and ceilings Leave all windows open for through ventilation at all times

To answer your question properly! Firstly yes you can paint normal emulsion over the undercoat as long as it has dried properly. Regarding the smell, the fumes are given off as the paint dries and in an oil based paint they are quite unpleasant (I refuse to use it for my customers). usually they will lessen once you get coats of paint on top but you might still smell it for a while. There is an alternative but it's a bit of extra work for you - and expense. There is a product called Zinsser BIN (you can get it in B&Q) that is a stain blocker and also seals in smells such as you are experiencing. However it can be tricky to work with as it is meths based and dries VERY fast. Use a brush on the edges and roller on the rest. The meths means it has a strong smell while it is wet but they are not toxic fumes and they will stop fairly quickly. You will also need to wash the brush and roller in meths but to be honest, you are probably better to just let them dry and then thrown them out. Once you have the BIN primer on the walls you can put your emulsion on. Whether you need one or two coats depends how good the paint is so use a trade paint rather than a retail paint - it will have more pigment. Good luck.

You can paint emulsion on top of oil based under coat but you have to leave undercoat to dry few days İf your walls stained or greasy the best product is apply ZİNSSER BİN on walls with roller than you can put any Paint on top with no problems