Ujeni,
I agree with you that Glyptol improves the circulation of the oil, but there we not speak of an engine of competition with of very high-performance and alloys for the foundry of these aluminum engine is of excellent quality, fragile and breakable but certainly not porous and you will notice that there is no budding of the aluminum in surfaces even on the engines which were stored and abandoned outside in the rain for years and years and that it is good the sign that the aluminum of these engine is not porous..
On the other hand, during the restoration of crankcases, it is necessary to clean them but especially not to clean them completely inside and it is necessary to keep this yellowish patina trained by the oil and the time which protects the aluminum.
Personally I would not take the risk of making paint has the inside of the engine which can disintegrate at any time on certain places even if Vic World recommends him..
Then, you make as you think best!!