Having just redecorated my home, using water based paints for the interior, I sympathise with your predicament.
In short, i found it impossible to duplicate the finish I got (on MDF furniture I'd built) using a spray gun. However, I did get very good results using a roller and brush to lay-off the paint - as rodders outlined. After some research and past experience I did what follows.
The challenge I found is to work 'smart' and quickly. The main problem is that the paint starts to dry too quickly, before it has had a chance to self-level, leaving the marks from the tool used - bubbles with foam rollers; lines with a brush. To combat this there are various 'tricks', most of which I tried.
You can add an additive, such as floetrol or XIM latex extender. Both are meant to extend the paint's wet edge and improve flow, thus eliminating the roller/brush marks. I tried the XIM, both alone and with some thinning (just water - upto 5-10%). I detected some improvement but don't feel I can wholly recommend the XIM. Another 'trick' is to use a fine mist spray gun - like the garden sprays or spray used by hairdressers to wet hair - and spray the furniture with a fine mist (of water) immediately before applying the paint. This worked well but you do need to be careful not to overwet or use a spray that sprays droplets - you want a fine mist.
Conditions are also key - hot/dry days make the paint dry quickly, so the opposite (higher relative humidity and cooler) are better for extending the paints 'workability'.
Overall, I got best results when using a 4" roller (foam and fibre used) to spread the paint quickly and evenly but without worrying about finish - just get an even coating on. Then, immediately, use a quality dry brush to gently 'lay it off' i.e. smooth the finish. I used a Wooster synthetic brush and recommend those. By dry I mean no paint but better to wet the brush with water and remove the excess so it's just damp. This helps prevent the paint clogging up the fibres - an occasional rinse/clean won't hurt but do remove the excess water. The laying off should be done with single long strokes with minimal overlap e.g. full length of your wardrobe's sides. If mouldings are a feature then generelly best to do those first and then the flat panels, aiming to work in sequence so as to keep the painted edge wet.
Finally, if you're able to move the furniture being painted so that the side being painted is horizontal then gravity will help to smooth the paint and avoid runs. You may even be able to thin the paint to as runny as possible so that it flows more quickly/smoothly. This will mean delay whilst you're waiting for one side to dry before it can be moved.
HTH. Mike
