The order of exposure makes no difference whatsoever when making the final print.
When making test strips it is best to determine the dominant exposure first.
For low contrast negatives (making a high contrast print) first determine the high contrast (magenta) exposure for the desired shadows, then find the right exposure for the highlights with the low contrast filter.
Conversely, for high contrast negatives (low contrast print) first determine the low contrast (yellow) exposure for the highlights, then move on to the shadows.
The reason for this is that the dominant exposure will have an effect on the other end of the tonal scale: A long high contrast/shadows (magenta) exposure will have some effect on the highlights, but the short low contrast/highlights (yellow) exposure will have no effect on the shadows; A long low contrast (yellow) exposure will have some effect on the shadows but the shorter shadow (magenta) exposure won't effect the highlights.
Experienced photographers often find themselves making lower contrast negatives (slightly overexposed and underdeveloped) and higher contrast prints. Generous film exposure is always a good idea. But, just as importantly, is the increase in linearity of the HD curve at higher contrast grades. Low contrast MG filtration invariably has flat spots in the curve, leading to poor detail in certain tones. If you print at -1 or 0 then you will find that detail disappears in the middle/dark greys - there is just a pool of fog where detail should be.
For more information on this see the Darkroom Automation application note:
http://www.darkroomautomation.com/support/appnotevcworkings.pdf
As for cold-light heads, well, they are just a can of worms when it comes to this issue. To keep prints consistent it is best to keep the head on all the time - only turn it off for loading the paper and while the paper is in the developer. This keeps the lamp hot (so much for 'cold' light ... of course, if you kept an incandescent head on all the time there would be a distinct smell of burning insulation after a while). Incandescent heads have a slight drift as they warm up - light output increases by about 0.05 stops over a period of a few minutes.