A trick I did with my Daytona to save me time was I kept a set of wheels on the base. The wheels don't have the be the actual wheels you plan to use, but so long as they are of the desired size. If the stock wheels are the ideally-sized wheels, that's even better as you may not even need to take them out of the prongs yet.. Make sure the alignment is good, that you don't have crooked axles or wheels that aren't perpendicular to the wheelbase. You can use something to help hold the axle in place if need be.
Once all that is perfect, I take tape and I start wrapping the tires, creating a roll of it. The idea here is that the wheel will mask off the fender well area to save you the trouble of having to sculpt and shape that area to perfect roundness. The thickness of the roll of tape you make will literally become the gap between the wheels and the fender once everything is done. Once that's decided, put the base back onto the casting and begin applying the putty. I've no trick for the rest of this. It's all eyeballing from here on forth.
for a buck
