The start point for DIY brickwork is to draw the brick pattern (the bond); in other words to draw the lines of mortar. At 4mm scale, bricks are about 3mm long, and about 1mm high. You will need to use the drawing software (not the painting software) to draw the lines accurately. The first stage is to use guidelines or a similar tool to help draw accurately.
In CorelDraw setting up guidelines is straightforward; figure 1a shows a few guidelines at 1mm centres horizontally, and 1.5mm vertically.
Using the 'snap to guidelines' facility we can now draw a couple of bricks accurately (figure 1b). You may need to experiment to get the line thickness right.
Using more guidelines we can copy and paste the first couple of bricks (figure 1c), and continue to copy/paste until we have a large enough area covered. At this stage it's worth exporting the drawing to the paint software (see last paragraph below), to make sure it all looks ok.
Figure 1d shows stretcher bond (for most modern buildings). You need to cover a large enough area to cover at least the largest wall of your building.
Figures 1e and 1f show Flemish bond (older buildings), and English bond (for structural brickwork; bridges viaducts etc). The mess hut, used as an example in the following pages uses Flemish bond.
The next stage is to export your drawing in a format that your photo software can read; a bitmap format of some sort. Corel has its own cpt format, which can be exported from CorelDraw, and read by Photopaint. When exporting you will need to know how many dots per inch (dpi) to use. This is effectively a measure of how detailed your drawing will be. 1200 dpi would be ideal, but will create a very large file (30 or 40 Mb) which will be too much for most computers to handle. 300 dpi is not enough, but 600 dpi is about right. Draw the mortar as black, but export the drawing in 24 bit colour. Once you've done this stage, you've done it for any the building you might want to build.