by mike-s » Sat Nov 29, 2008 8:35 pm
Sand back any paint 5-8mm from the edge of the join on both peices.
Fit the peices you want to weld together, use a dremel style grinding/abrasive tool and grind a v-groove in the surface of the break (that does NOT go all the way through and at around a 45' angle works best) so there is a better chance for it to fill/bind.
Use something like electrical tape for long grooves (bluetack works surprisingly well too) along the underside of the groove to stop the binder from leaking through while you attempt to get it to set.
Scoop a little of the plastic powder into the groove you have ground (i find using a straw with the edge cut at about a 15-20' angle, thats about a 1 inch face on the cut to be perfect for measuring such small proportions.) until it rises 0.5-1mm above the surface of the groove.
Then use the dropper and be very very VERY careful on your usage of the fluid, one fully squeezed drop can do about a 5x5-7x7mm area on a 2-3mm deep ground surface, but it is extremely easy to overdo it, this is the bit you have to practice.
Once it has cured (give it 10-15mins to cure at about 25'c+) and you have filled any gaps in with more powder and fluid to level it out then flip it over and grind the other side and repeat the process to perform a uniform surface repair.

If it hurts, you aren't doing it right.